Friday, November 20, 2009

NFS on Debian/Ubuntu

Installation of NFS on server

Considering how powerful NFS is and the flexibility it gives you it is amazingly simple to set up. I expected it to be on a par with setting up Samba which can be a complete nightmare. Typically when setting up Samba one would use Swat or another configuration tool. With NFS set us is as easy as entering the paths you want exported into /etc/exports and making sure the correct packages are installed.

There are two implementations of NFS one runs in kernel space (nfs-kernel-server) the other in user space (nfs-user-server). The kernel space implementation is faster and more stable but if something goes wrong it could bring your box down. In reality the kernel space NFS implementation very rarely fails. I have been running it for years (and on at least one occasion for 150 days straight) and have had it fail only a couple of times. The times it did fail it simply needed restarting. In fact the only way I have even managed to get it to make a noise is when I had a box with a network card that was on the way out. The port on the card was bad which caused it to repeatedly drop and re-aquire the network sometimes several times a minute. After a few hours of that NFS would sometimes start to refuse new connections.

As well as the server you will need portmap. Fortunately if you chose NFS when you first installed the server you will have all the required packages already installed, configured and running.

One important point to remember when setting up NFS is to make sure that the user id (uid) of the user on the server matches the uid of the user on the local machine. NFS has no way of mapping "fred" on the local machine to "fred" on the server other than by relying on the uids being the same. Typically when you create a user the uid given is just the next one available but you can specify it explicitly.

Once you have made the required entries in /etc/exports you need to tell the NFS server about them. Typically I restart all three required utilities (portmap, nfs-kernel-server and nfs-common) as it is generally the best way to make sure everything is working correctly. See the section below on restarting NFS.

Step 0: Installation of NFS-server and NFS-client
# apt-get install nfs-kernel-server nfs-common portmap
apt-get install nfs-common portmap

Step 1: Export directories on server
At server machine, export the directory in /etc/export file
# /etc/exports: the access control list for filesystems which may be exported
# to NFS clients. See exports(5).

Step 2: Restarting NFS on server

nfs-server:/samba#/etc/init.d/portmap start
nfs-server:/samba#/etc/init.d/nfs-kernel-server start
nfs-server:/samba#/etc/init.d/nfs-common start

Verify NFS is runnning
nfs-server:/samba# rpcinfo -p
program vers proto port
100000 2 tcp 111 portmapper
100000 2 udp 111 portmapper
100004 2 udp 878 ypserv
100004 1 udp 878 ypserv
100004 2 tcp 881 ypserv
100004 1 tcp 881 ypserv
100009 1 udp 880 yppasswdd
600100069 1 udp 883 fypxfrd
600100069 1 tcp 885 fypxfrd
100007 2 udp 892 ypbind
100007 1 udp 892 ypbind
100007 2 tcp 895 ypbind
100007 1 tcp 895 ypbind
100003 2 udp 2049 nfs
100003 3 udp 2049 nfs
100021 1 udp 32868 nlockmgr
100021 3 udp 32868 nlockmgr
100021 4 udp 32868 nlockmgr
100005 1 udp 709 mountd
100005 1 tcp 712 mountd
100005 2 udp 709 mountd
100005 2 tcp 712 mountd
100005 3 udp 709 mountd
100005 3 tcp 712 mountd
100024 1 udp 32869 status
100024 1 tcp 58711 status

Step3: Mounting NFS drives on Client
Add location with drive and options.
:  nfs  0 0

# Mounts from other hosts

nfs-server:/home /home nfs rw,rsize=32768,wsize=32768,hard,intr,async 0 2

Mount also on command line
client:/# mount -t nfs nfs-server:/home /home

Verification of mounting the drive.
On Client verify the mount point

client:/# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 2.8G 2.1G 578M 79% /
tmpfs 126M 0 126M 0% /lib/init/rw
udev 10M 52K 10M 1% /dev
tmpfs 126M 0 126M 0% /dev/shm
nfs-server:/home 123G 105G 12G 90% /home


Monday, November 9, 2009

Upgrading Subversion in Ubuntu 9.10 server

Step 1:Install the subversion
apt-get install subversion libapache2-svn

Step 2: Create the repository

svnadmin create /svn

Edit the directory

# Uncomment this to enable the repository,
DAV svn
# Set this to the path to your repository
SVNPath /svn
# Uncomment the following 3 lines to enable Basic Authentication
AuthType Basic
AuthName “Subversion Repository”
AuthUserFile /etc/apache2/dav_svn.passwd

Require valid-user

Save and exit the file

Creation of user
htpasswd -cm /etc/apache2/dav_svn.passwd imran
New password:
Re-type new password:
Adding password for user imran

Enable ssl (if required)
#a2enmod ssl

This will enable the ssl if you have problem to set it.

Export by :Dumping the existing repository
root@jupiter:/svn# svnadmin dump svn > reposdump.dmp
Import by:
root@saturn:/srv# svnadmin load srv-jupiter < /home/imran/reposdump.dmp

Tuesday, November 3, 2009

Intrusion Detection (Snort) fixation in IPCOP Firewall 1.4.21

After installing the IPcop got the following error messages

When running update the Error is:
HTTP::Response=HASH(0x82a3c14)->code registered md5
When running download the Error is:

The reason is that now publish rules now on current branch that are no more compatible with snort-
We have manually add the current branch, to - date it is 2. You can find on snort if you have your account on under My Account-->My Oinkcodes along with the code (You must have account at snort to access code and use snort in IPCOP).

Here is a solution, it is a manual fixation in the code.

Open the /usr/local/bin/ in and editor.
root@firewall:/etc/snort # nano /usr/local/bin/
Change the value to 2.8 at line no 55.
my $rulesbranch="2.8"; # version should match snort branch version

Save the change.
Remember you must have to add the oink code in IPCOP--> Services-->INTRUSION DETECTION.
Save-Apply-Refresh update list-Download Rullset.

It should work, no update rull-set failure or MD5 checksum error.

Friday, September 25, 2009

Wireless Chanel list in Ubuntu

Step 1: Install/Enable your Wireless Card

Step 2: Scan the media using 'iwlist scan'
root@imran-laptop:~/Desktop# iwlist scan
lo Interface doesn't support scanning.
eth0 Interface doesn't support scanning.
wlan0 Scan completed :
Cell 01 - Address: 00:1B:11:5A:BC:48
Frequency:2.412 GHz (Channel 1)
Quality=43/70 Signal level=-67 dBm
Encryption key:on
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s
Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 18 Mb/s; 24 Mb/s
36 Mb/s; 48 Mb/s; 54 Mb/s
Extra: Last beacon: 2732ms ago
IE: Unknown: 000770696E67636F6D
IE: Unknown: 010482848B96
IE: Unknown: 030101
IE: Unknown: 2A0100
IE: Unknown: 32088C129824B048606C
IE: IEEE 802.11i/WPA2 Version 1
Group Cipher : TKIP
Pairwise Ciphers (2) : TKIP CCMP
Authentication Suites (1) : PSK
IE: WPA Version 1
Group Cipher : TKIP
Pairwise Ciphers (2) : TKIP CCMP
Authentication Suites (1) : PSK
IE: Unknown: DD180050F2020101000003A4000027A4000042435E0062322F00
IE: Unknown: DD1E00904C334E101FFFFF000000000000000000000000000000000000000000
IE: Unknown: DD1A00904C340105070000000F000000000000000000000000000000
IE: Unknown: 2D1A4E101FFFFF000000000000000000000000000004000000000000
IE: Unknown: 3D160105030000000F000000000000000000000000000000
Cell 02 - Address: 00:19:5B:47:45:E5
Frequency:2.417 GHz (Channel 2)
Quality=57/70 Signal level=-53 dBm
Encryption key:on
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
12 Mb/s; 24 Mb/s; 36 Mb/s
Bit Rates:9 Mb/s; 18 Mb/s; 48 Mb/s; 54 Mb/s
Extra: Last beacon: 2776ms ago
IE: Unknown: 000B4F776572612D4775657374
IE: Unknown: 010882848B960C183048
IE: Unknown: 030102
IE: Unknown: 2A0100
IE: Unknown: 32041224606C
IE: WPA Version 1
Group Cipher : TKIP
Pairwise Ciphers (2) : TKIP CCMP
Authentication Suites (1) : PSK
IE: Unknown: DD0900037F01010006FF7F
IE: Unknown: DD0C00037F020101000002A34000


Step3: Change permission of script to execute , Script is at the bottom.
root@imran-laptop:~/Desktop# chmod -R +x

Step 4: Run the Script
root@imran-laptop:~/Desktop# ./
+ --- + ------------------------------ + ------- + -------- + --- + ------ + --------- + ---------------------- + ----------------- +
| # | Name | Quality | Sig Lvl | Enc | Enc T. | Auth T. | Channel | AP MAC |
+ --- + ------------------------------ + ------- + -------- + --- + ------ + --------- + ---------------------- + ----------------- +
| 1 | "pingcom" | 55/70 | -55 dBm | on | WPA v1 | PSK | 2.412 GHz (Channel 1) | 00:1B:11:5A:BC:48 |
| 2 | "Owera-Guest" | 57/70 | -53 dBm | on | WPA v1 | PSK | 2.417 GHz (Channel 2) | 00:19:5B:47:45:E5 |
| 3 | "Difi-Gjestenett" | 50/70 | -60 dBm | off | WEP | N/A | 2.412 GHz (Channel 1) | 00:13:F7:CA:25:D9 |
| 4 | "DVG-5802S" | 53/70 | -57 dBm | on | WPA v1 | PSK | 2.427 GHz (Channel 4) | 06:21:94:00:54:D4 |
| 5 | "Difi-Gjestenett" | 38/70 | -72 dBm | off | WEP | N/A | 2.437 GHz (Channel 6) | 00:13:F7:CA:25:D4 |
| 6 | "ft-test" | 53/70 | -57 dBm | on | WPA v1 | PSK | 2.447 GHz (Channel 8) | 0E:21:94:00:54:D4 |
| 7 | "Einar Aaland's Network" | 44/70 | -66 dBm | on | WPA v1 | PSK | 2.457 GHz (Channel 10) | 00:1F:5B:88:54:13 |
| 8 | "ap2" | 43/70 | -67 dBm | on | WEP | N/A | 2.422 GHz (Channel 3) | 00:19:5B:47:65:F3 |
| 9 | "pingcom" | 43/70 | -67 dBm | on | WPA v1 | PSK | 2.432 GHz (Channel 5) | 00:1B:11:5C:82:01 |
| 10 | "Difi_Adm" | 31/70 | -79 dBm | on | WPA v1 | 802.1x | 5.54 GHz (Channel 108) | 00:24:C4:F9:16:3F |
| 11 | "Difi_Adm" | 32/70 | -78 dBm | on | WPA v1 | 802.1x | 2.437 GHz (Channel 6) | 00:24:C4:F9:16:30 |
+ --- + ------------------------------ + ------- + -------- + --- + ------ + --------- + ---------------------- + ----------------- +

Her is the script, this is written by Timothy Mills, downloaded from Internet, thanks to Timothy Mills, we just did some changes to have MAC addresses or APs. You can copy this and save it as '' and change permission to execute..
# Author: Timothy Mills
# Date : 8 - 4 - 08
# File :
# takes the output of 'iwlist scan' and makes it in an easier
# to read format for those of us who still deal with the terminal :)


#Run the command and suppress error output
$iwlistOut = `iwlist scan 2> /dev/null`;

@myLines = split("\n", $iwlistOut);
@cellArr = [];

printFin("#", "Name", "Quality","Sig Lvl", "Enc", "Enc T.", "Auth T.", "Channel", "AP MAC");

$currNum = 0;

foreach (@myLines)
if ($_ =~ "Cell [0-9][0-9]")
if ($currNum > 0)
printFin($currNum, $name, $quality, $sigLvl, $enc, $encType,
$authType, $chn, $mac);


$cellArr[$currNum] = $cellArr[$currNum]."$_"."\n";

if ($_ =~ "ESSID")
elsif($_ =~ "Frequency")
elsif($_ =~ "Address:")

elsif($_ =~ "Encryption key")
elsif($_ =~ "Quality=[0-9]+/[0-9]+")
elsif($_ =~ "IE: WPA .+ [0-9]")
elsif($_ =~ "Authentication Suites")


if ($currNum > 0)
printFin($currNum, $name, $quality, $sigLvl, $enc, $encType, $authType, $chn, $mac);
print("No scan results :'( \n");

if (scalar @ARGV == 1)
$myNum = ($ARGV[0] =~ "[0-9]+");

print $cellArr[$ARGV[0]] if($myNum && ($ARGV[0]>0 && $ARGV[0] <= $currNum)); } sub helpCheck () { foreach(@ARGV) { helpMsg() if ($_ =~ "--help"); } if (scalar @ARGV == 1 && !($ARGV[0] =~ "[0-9]+")) { helpMsg(); } elsif (scalar @ARGV > 1)

sub helpMsg ()
printf("Usage: [network number] \n\n");
printf("wiscan is used to make the output of 'iwlist scan' be more readable"

printf("from within a terminal. By using the optional argument you may \n");
printf("get the full output for a network from 'iwlist scan'\n\n");

printf("EXAMPLES: \n");
printf("1: ./ -- Lists all wireless networks within range\n");
printf("2: ./ 2 -- Shows full output for second wireless network entry \n in the output of\n");


sub printFin()
printf("| %-3s | %-30s | %-7s | %-8s | %-3s | %-6s | %-9s | %-22s | %-17s |\n", $_[0],
$_[1], $_[2], $_[3], $_[4], $_[5], $_[6], $_[7],$_[8]);

sub printHeading()
printf("+ %-3s + %-30s + %-7s + %-8s + %-3s + %-6s + %-9s + %-22s + %-17s +",
"---", "------------------------------", "-------", "--------", "---", "------", "---------","----------------------","-----------------");


sub varInit()
$name = "";
$quality = "";
$sigLvl = "";
$enc = "";
$chn = "";
$mac = "";
$encType = "WEP";
$authType = "N/A";

sub handleEncType ()
$encType = "WPA v".($_ =~ ".*[0-9]");

sub handleQuality ()
$qual = $_[0];

@qualArr = split(" ", $qual);

$quality = (split("=", $qualArr[0]))[1];
$sigLvl = (split("=", $qualArr[2]))[1]." dBm";

sub handleChn ()
$chn = (split(":", $_[0]))[1];

sub handleMAC ()
$mac = (split(": ", $_[0]))[1];

sub handleKey ()
$enc = (split(":", $_[0]))[1];

sub handleName ()
$name = (split(":", $_[0]))[1];

sub handleAuthType ()
$authType = (split(" ", $_[0]))[4];

Tuesday, September 15, 2009

DHCP-RELAY Agent in Ubunt 8.04 hardy

I am using I386 Machine with fresh install of ubuntu 8.04 Server and two interfaces.
eth2----use to listen dhcp request

Step 1: Install the dhcp3-package
First add following in /etc/apt/sources.list
root@ubuntu:~# nano /etc/apt/sources.list

deb hardy-security main universe

add and exit,then
root@ubuntu:~# apt-get install dhcp3-relay
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
0 upgraded, 1 newly installed, 0 to remove and 7 not upgraded.
Need to get 103kB of archives.
After this operation, 274kB of additional disk space will be used.

During Installation it will ask you,
a) DHCP server IP address e.g your dhcp server address and
b) Interface which you will listen for dhcp requests e.g eth2.

Step 2: Enable forwarding.
root@ubuntu:~# echo 1 > /proc/sys/net/ipv4/ip_forward
root@ubuntu:~# echo 1 > /proc/sys/net/ipv4/tcp_syncookies
root@ubuntu:~# echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts

Step 3: Testing

Attach cable on eth2 to a pc and wait for responce

Thursday, September 10, 2009

Setup ITERATIVE DNS in Ubuntu 8.04 Server

Step 1: Fresh Install the Ubuntu server with option of DNS server during installation or you can install DNS latter in step 2.

Step 2: Install DNS if not installed before
root@ins# apt-get install bind9

Step 3: Edit /etc/bind/named.conf.options to disable recursion.

By default the recursion is enables(yes), you can add /uncomment the follwoing line in option field.

//recursion yes; //default

recursion no;

root@ins:/etc/bind# nano named.conf.options

options {
directory "/var/cache/bind";

// If there is a firewall between you and nameservers you want
// to talk to, you might need to uncomment the query-source
// directive below. Previous versions of BIND always asked
// questions using port 53, but BIND 8.1 and later use an unprivileged
// port by default.

// query-source address * port 53;

// If your ISP provided one or more IP addresses for stable
// nameservers, you probably want to use them as forwarders.
// Uncomment the following block, and insert the addresses replacing
// the all-0's placeholder.

// forwarders {
// };

recursion no;
auth-nxdomain no; # conform to RFC1035
listen-on-v6 { any; };

Step 4: Restart the bind
root@ins:/etc/bind# /etc/init.d/bind9 restart

Step 5: Testing

You can run wireshark in your machine and try to ping a host e.g ping

In trace you will see the response from dns server, expand the Domain Name System, Flags and Authoritative Server list can be seen.

Wednesday, September 9, 2009

iRED Mail Installation on Ubuntu Server 8.04

Installation of useful tools.

root@redmail:~# apt-get install acl wget dialog

Copy following to /etc/apt/sources.list
root@redmail:~# nano /etc/apt/sources.list

deb hardy main
deb-src hardy main
Add key, you can replace your key, I used this "61270A939E324B12" and update.

root@redmail:~#apt-key adv --keyserver --recv-keys 61270A939E324B12
Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /etc/apt/secring.gpg --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --keyserver --recv-keys 61270A939E324B12
gpg: requesting key 9E324B12 from hkp server
gpg: key 9E324B12: public key "Launchpad PPA for LI Daobing" imported
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
root@redmail:~# apt-get update

Add mount option 'acl' in /etc/fstab
which contains '/etc/' directory if it doesn't there yet. Copy it as a new line, and comment the old one, add 'acl' like below.
    # /dev/sda1
    UUID=63b655fe-5959-46bc-b9db-09ad2d746b78 / ext3 relatime,errors=remount-ro 0 1

    Note: It seems you don't need to add this 'acl' option in /etc/fstab if you use VPS which hosted by OpenVZ, because you can't edit /etc/fstab file, and it already supports acl.

Remount the mount point which contains '/etc/' directory. e.g. '/':
    root@iredmail:/var/tmp/iRedMail-0.5.0# mount -o remount,rw,acl /

Download the package " iRedMail-0.5.0.tar.bz2 " from
and move it to /var/tmp directory.
#cd /var/tmp
#tar -xvf iRedMail-0.5.0.tar.bz2
#cd iRedMail-0.5.0/pkgs

Run the script

This will fetch the required packages from source, please make sure that your Internet is working ok.

root@redmail:/var/tmp/iRedMail-0.5.0/pkgs# bash
<> Creating necessary directories ...
<> ==================== Fetching Source Tarballs ====================
<> * 1/16:
<> * 2/16:
<> * 3/16:
<> * 4/16:
<> * 5/16:
<> * 6/16:
<> * 7/16:
<> * 8/16:
<> * 9/16:
<> * 10/16:
<> * 11/16:
<> * 12/16:
<> * 13/16:
<> * 14/16:
<> * 15/16:
<> * 16/16:
<> Validate Packages via md5sum ... [ OK ]
<> Checking necessary command/package: dialog/dialog ...
<> Checking necessary command/package: setfacl/acl ...
* All tasks had been finished Successfully. Next step:
* # cd ..
* # bash

Make Sure devcot is installted
root@redmail:/var/tmp/iRedMail-0.5.0/pkgs# apt-cache policy dovecot-common dovecot-pop3d dovecot-imapd | grep 'Candidate'
Candidate: 1:1.1.11-0ubuntu4~hardy2
Candidate: 1:1.1.11-0ubuntu4~hardy2
Candidate: 1:1.1.11-0ubuntu4~hardy2

Start Installation
root@redmail:/var/tmp/iRedMail-0.5.0# bash

It will ask question about path of directory, options, etc.... press next next and Y at the end.

It will installed every thing you need with options you select.

Component URL Access via HTTP Access via HTTPS
Roundcube webmail http://your_server/mail/ (or /webmail, /roundcube) YES YES
SquirrelMail webmail http://your_server/squirrelmail/ (or /squirrel) YES YES
PostfixAdmin https://your_server/postfixadmin/ NO YES
phpMyAdmin https://your_server/phpmyadmin/ (or /mysql) NO YES
phpLDAPAdmin https://your_server/ldap/ (or /phpldapadmin) NO YES
Awstats https://your_server/awstats/ NO YES

Now you can login and send your first mail to any other account for testing.


Tuesday, September 1, 2009

How to make Ubuntu/Debian as a router

Here is your Ubuntu serve box with two interfaces,
Note: Your Internet is running using eth0.
Step1: Install DHCP Server

#apt-get install dhcp3-server

Step 2: Configure the DHCP server

Edit the /etc/dhcp3/dhcpd.conf file and add your domain, dns, ip range and other options.

option domain-name "";
option domain-name-servers, xx.xx.xx.xx;
# Internal network
subnet netmask {
option broadcast-address;
option routers;
default-lease-time 600;
max-lease-time 7200;

Step 3: Configure the Internal interface (eth2) with static IP.
Edit the /etc/network/interfaces file and add following

iface eth2 inet static

Step 4: Restart network and verify the eth2 interface's IP.

#/etc/init.d/network restart

check ip by ifconfig eth2, it will have ip, if not please restart the interface/netwrok service, you can also restart your machine if it is not in production environment.

Step 5: Restart the DHCP server.

#/etc/init.d/dhcp3-server restart

If every thing is ok, it should run successfully,
Note: If your interface does not have any IP it might give error and does not restart, first configure you internal interface.

Step 6: Test the DHCP server.

connect the cable on interface eth2 and other side to your second pc, you will get the IP from 192.168.50.x range.
Open the syslog messeges with
#tail -f /var/log/syslog
of your debian box, it will also notify with leased ip and detail of requested machine.

Step 7: Enable forwarding
# cat /proc/sys/net/ipv4/ip_forward
# echo 1 > /proc/sys/net/ipv4/ip_forward

or open the file manually and uncomment

# nano /etc/sysctl.conf

net.ipv4.ip_forward = 1

Step 8: Add IPTABLES rule for NAT

Type following at command line

#iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

Step 9: Final Testing

Your second Pc attached to LAN have internal ip, ping to, it should get reply, if not review and trouble shoot carefully.

imran@imran-laptop:~$ ping
PING ( 56(84) bytes of data.
64 bytes from ( icmp_seq=1 ttl=52 time=30.7 ms
64 bytes from ( icmp_seq=2 ttl=52 time=30.2 ms
64 bytes from ( icmp_seq=3 ttl=52 time=30.3 ms
--- ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 30.298/30.451/30.729/0.242 ms


Thursday, August 6, 2009

Network+ Cram Sheet


  • Peer-to-peer networks are useful for only relatively small networks. They are often used in small offices or home environments.
  • Client/server networks, also called server-centric networks, have clients and servers. Servers pro video centralized administration, data storage, and security. The client system requests data from the server and displays the data to the end user.
  • The bus network topology is also known as a linear bus because the computers in such a network are linked together using a single cable called a trunk, or backbone.
  • If a terminator on a bus network is loose, data communications might be disrupted. Any other break in the cable will cause the entire network segment to fail.
  • In a start configuration, all devices on the network connect to a central devices, and this central devices creates a single point of failure on the network.
  • In the ring topology, the network layout forms a complete ring. computers connect to the network cable directly or. more commonly, through a specialized network device.
  • Breaking the loop of a ring network disrupts the entire network.
  • The mesh topology requires each computer on the network to be individually connected to every other device. This configuration provides maximum reliability and redundancy for the network.
  • Wireless networks use centralized device known as wireless access point (WAP).
  • 802.2, the LLC sublayer, defines specifications for the Logical Link Control (LLC) sublayer in the 802 standard series.
  • 802.3 defines the carrier-sense multiple-access with collision detection (CSMA/CD) media access method used in Ethernet networks. This is the most popular networking standard used today.
  • 802.5 defines Token Ring networking.
  • 802.11 defines standards for wireless LAN communication.
  • Many factors cause EMI, including computer monitors and fluorescent lighting fixtures.
  • Copper-based media are prone to EMI whereas fiber-optic cable is resistant to it.
  • Data signals may also be subjected to something commonly referred to a crosstalk. which occurs when signals from two cables, or from wires within a single cable, interfere with each other.
  • The weakening of data signals as they traverse the media is referred to a attenuation.
  • Half-duplex mode allows each device to both transmit ans receive, but only on of these processes can occur at a time.
  • Full-duplex mode allow devices to receive and transmit simultaneously. A100 Mbps network card in full-duplex mode can operate at 200Mbps.


  • Thin coax is only .25 inches in diameter and has a maximum cable length of 185 meters (600 feet approx.)
  • Thick coax networks use a device called a tap to connect a smaller cable to the thick coax back-bone. This coax has a 500-meter cable length.
  • Attachment unit interface AUI ports are network interface ports that are often associated with thick coax (10Base5) networks. The AUI port is a 15-pin socket to which a transceiver is connected.
  • SC and ST connectors are associated with fiber cabling. ST connectors offer a twist-type attachment and SC connectors are push-on connectors.
  • RJ-45 connectors are used with UTP cable.


  • 10Base2, sometimes called Thinnet or Thin Ethernet, is the 802.3 specification for a network that uses thin coaxial cable (that is , RG-58 cable).
  • 10Base2 specifies a maximum speed of 10Mbps ans uses BNC barrel and BNC T connectors to connect the cable and computers. At the physical ends of each cable segment, a 50-ohm terminator absorbs the signal, thus preventing signal reflection.
  • The 10Base2 standard specifies a limit of 185 meters per segment (600 feet approx.)


  • Token Ring Networks use special devices called multi-station access units MSAUs to create the network.
  • A straight-through cable is used to connect systems to the switch or hub using the MDI-X ports.
  • In a crossover cable, Wires 1 and 3 Wires 2 and 6(1326) are crossed.
  • Bridges are used to divide networks and thus reduce the amount of traffic on each network.
  • RIP is distance vector dynamic routing protocol for both TCP and IPX.
  • A MAC address is 6-byte(48bits) hexadecimal address that lets a NIC be uniquely identified on the network. The first three bytes (00:D0:59) represent to manufacturer, last three are Universal LAN MAC address, which makes interface unique.
Mapping network devices to the OSI model:
  • HUB-------Physical (Layer 1)
  • SWITCH--Data-Link (Layer 2)
  • BRIDGE--Data-Link (Layer 2)
  • ROUTER-Network (Layer 3)
  • NIC--------Data-Link (Layer 2)


  • As data is passed up or down through the OSI model structure, headers are added,encapsulation (going down) or removed,de-capsulation (going up), at each layer.
  • The Application Layer provides access to the network for applications and certain end-user functions. It displays incoming information and prepares outgoing information for network access.
  • The Presentation Layer converts data from the Application Layer into a format that can be sent over the network. It converts data from the Session Layer into a format that can be understood by the Application Layer. It also handles encryption and decryption of data and provides compression and decompression functionalities.
  • The Session Layer synchronizes the data exchange between applications on separate devices. It handles error detection and notification to the peer layer on the other device.
  • The Transport layer establishes, maintain, and breaks connections between two devices. It determines the ordering and priorities of data. It also performs error checking and verification and handles retransmissions, if necessary.
  • The Network Layer provides mechanisms for the routing of data between devices across single or multiple network segments and handles the discovery of destination systems and addressing.
  • The Data-Link Layer has two distinct sub-layers: LLC and MAC. It performs error detection and handling for the transmitted signals. It also defines the method by which the medium is accessed and defines hardware addressing through the MAC sublayer.
  • The Physical Layer defines the physical structure of the network. It also defines voltage/signal rates and the physical connection method, as well as the physical topology.


  • CLASS A uses first octet for network rest three for hosts. Class B uses two octet for Network and 2 for hosts and Class C uses first three for network and last 1 for hosts.
  • Class A from 1 to 126 with default subnet
  • Class B from 128 to 191 with default subnet mask
  • Class C from 192 to 223 with default subnet mask of
  • The 127 network ID is reserved for local loopback.
  • Application protocol maps to the application presentation, and session layers of OSI model. Application protocols include AFT,FTP,TFTP,NCP and SNMP.
  • Transport protocols map to the Transport layer of the OSI model and are responsible for transporting data across the network. Transport protocols include ATP, NetBEUI, SPX, TCP and UDP.
  • The NetBEUI protocol uses names as addresses.
  • Network protocols are responsible for providing the addressing and routing information. Network protocols include IP. IPX and DP.
  • The TCP/IP protocol suite is used by all major operating systems and is route-able protocol.
  • IPX/SPX protocol is associated with NetWare network and is route-able.
  • NETBEUI is used on Windows networks and is not route-able.
  • DHCP/BOOTP automatically assign IP addressing information.
  • DNS resolves host names to IP addresses.
  • NAT/ICS translates private network addresses into public network address.
  • WINS resolves NetBIOS names to IP addresses.
  • SNMP provides network management facilities on TCP/IP based networks.
  • In a network that does not use DHCP, you need to watch for duplicate IP addresses that prevent a user from logging onto the network.
  • Class A address uses only the first octet to represent the network portion.


  • The underlying technologies that enable the RAS process are dial-up protocols such as PPP and SLIP.
  • SLIP also does not provide error checking or packet addressing, so it can be used only in serial communications.
  • PPP provides several security enhancements compared to SLIP. The most important of these is the encryption of user names and password during the authentication process.
  • ICA protocol allows client systems to access and run application on a server, using the resources of the server, with only the user interface, key-strokes, an mouse movement being transferred between the client and server computers.
  • IPSec is designed to encrypt data during communication between two computers. IPSec operates at the Network layer of the OSI model and provides security for protocols that operate at higher layers.
  • SSL is a security protocol used on the Internet. Secure Web site URLs defing with https:// instead of http://. HTTPS connections require a browser to establish a secure connection. Secure SSL connections for Web pages are made through port 443 by default.
  • The security tokens used in Kerberos are knows as tickets.


  • RAID 0 offers no fault tolerance and improves I/O performance. It requires a minimum of two disks.
  • RAID 1, disk mirroring provides fault tolerance and requires two hard disks. Seprate disk controllers can be used as disk duplexing.
  • RAID 5, disk striping with distributed parity requires a minimum of three disks. The total size of a single disk being used for parity calculation.
  • In a full back all data is backed up. Full backups do not use the archive bit but do clear it.
  • Incremental backups back up all data that has changed since the last full or incremental backup. Uses and clears the archive bit.
  • Differential backups backup all data since the last differential backup. They use the archive bit but do not clear it.


  • VLANs are used to segment networks. This is often done for oranization of security puposes.
  • NAS is usedto offload data storage from traditional file servers. NAS devices are connected directly to the network and use the SMB and NFS application protocols.


  • To log on to a NetWare server, you might need a username, password, tree, and context.
  • Unix and Linux use the Network File System (NFS) protocol to provide file sharing capibilites between computers.
  • A password that uses eight case-sensitive characters with letters, numbers and special characters often makes a strong password.
  • Windows 2000 permissions include full control, modify, read and execute list folder contents read and write.
  • When a user can't access files that other users can, verify that correct permissions are set.
  • A firewall is a system or group of systems that controls the flow of traffic between two networks. A firewall often provides such services as NAT, proxy services and packet filtering.
  • A proxy server allows Internet access to be controlled. Having a centralized point of access allows for a great deal of contrl over the use of Internet.


  • You can PING the IP address of the local loop-back adapter by using the command ping this command is successful, you know that the TCP/IP protocol suite is installed correctly on you system and functioning.
  • tracert reports the amount of time it takes to reach each router in the path. It is useful tool for isolating bottlenecks in a network. ARP is the part of the TCP/IP suite whose function is to resolve IP


    addresses to the MAC address.
  • ARP operates at the Network layer of the OSI.
  • netstat is used to view both inbound and outbound TCP/IP network connections.
  • nbtstat is used to display protocol and statistical information for NetBIOS over TCP/IP connections.
  • ipconfig(Windows)/ifconfig(Linux) shows the IP configiguration information of all NICs instaled.
  • ipconfig /all is used to display detailed TCP/IP configuration information.
  • ipconfig /renew is used to refresh the IP.
  • When looking for client connectivity problems using ipconfig, you should ensure that the gateway is correctly set.
  • winipcfg is Windows95,98,Me equibalent of ipconfig command.
  • nslookup command is TCP/IP diagnostic tool used to troubleshoot DNS problems.


  • A wire crimer is a tool that you use to attach media connectors to the ends of cables.
  • Media testers, also called cable testers are used to test wheter a cable is working properly.
  • An optical cable tester performs the same basic function as a wire media tester, but on optical media.
  • The hardware loopback tests the outgoing signals of a device such as a network card.
  • If the LED on a network card is constantly lit, you might have chattering network card.

Common Networking Terms and Qustions

1. What are 10Base2, 10Base5 and 10BaseT Ethernet LANs
10Base2—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling, with a contiguous cable segment length of 100 meters and a maximum of 2 segments.
10Base5—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband google_protectAndRun("ads_core.google_render_ad", google_handleError, google_render_ad); signaling, with 5 continuous segments not exceeding 100meters per segment.
10BaseT—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling and twisted pair cabling.

2. Explain the difference between an unspecified passive open and a fully specified passive open

An unspecified passive open has the server waiting for a connection request from a client. A fully specified passive open has the server waiting for a connection from a pecific client.

3. Explain the function of Transmission Control Block

A TCB is a complex data structure that contains a considerable amount of information about each connection.

4. Explain a Management Information Base (MIB)

A Management Information Base is part of every SNMP-managed device. Each SNMP agent has the MIB database that contains information about the device's status, its erformance, connections, and configuration. The MIB is queried by SNMP.

5. Explain anonymous FTP and why would you use it

Anonymous FTP enables users to connect to a host without using a valid login and password. Usually, anonymous FTP uses a login called anonymous or guest, with the assword usually requesting the user's ID for tracking purposes only. Anonymous FTP is used to enable a large number of users to access files on the host without having to go to the trouble of setting up logins for them all. Anonymous FTP systems usually have strict controls over the areas an anonymous user can access.

6. Explain a pseudo tty
A pseudo tty or false terminal enables external machines to connect through Telnet or rlogin. Without a pseudo tty, no connection can take place.

7. Explain REX
What advantage does REX offer other similar utilities

8. What does the Mount protocol do
The Mount protocol returns a file handle and the name of the file system in which a requested file resides. The message is sent to the client from the server after reception of a client's request.

9. Explain External Data Representation

External Data Representation is a method of encoding data within an RPC message, used to ensure that the data is not system-dependent.
10. Explain the Network Time Protocol ?

11. BOOTP helps a diskless workstation boot. How does it get a message to the network looking for its IP address and the location of its operating system boot files
BOOTP sends a UDP message with a subnetwork broadcast address and waits for a reply from a server that gives it the IP address. The same message might contain the name of the machine that has the boot files on it. If the boot image location is not specified, the workstation sends another UDP message to query the server.

12. Explain a DNS resource record
A resource record is an entry in a name server's database. There are several types of resource records used, including name-to-address resolution nformation. Resource records are maintained as ASCII files.

13. What protocol is used by DNS name servers

DNS uses UDP for communication between servers. It is a better choice than TCP because of the improved speed a connectionless protocol offers. Of course, transmission reliability suffers with UDP.

14. Explain the difference between interior and exterior neighbor gateways
Interior gateways connect LANs of one organization, whereas exterior gateways connect the organization to the outside world.

15. Explain the HELLO protocol used for
The HELLO protocol uses time instead of distance to determine optimal routing. It is an alternative to the Routing Information Protocol.

16. What are the advantages and disadvantages of the three types of routing tables

The three types of routing tables are fixed, dynamic, and fixed central. The fixed table must be manually modified every time there is a change. A dynamic table changes its information based on network traffic, reducing the amount of manual maintenance. A fixed central table lets a manager modify only one table, which is then read by other devices. The fixed central table reduces the need to update each machine's table, as with the fixed table. Usually a dynamic table causes the fewest problems for a network
administrator, although the table's contents can change without the administrator being aware of the change.

17. Explain a TCP connection table

18. Explain source route

It is a sequence of IP addresses identifying the route a datagram must follow. A source route may
optionally be included in an IP datagram header.

19. Explain RIP (Routing Information Protocol)
It is a simple protocol used to exchange information between router.

20. Explain SLIP (Serial Line Interface Protocol)

It is a very simple protocol used for transmission of IP datagrams across a serial line.

21. Explain Proxy ARP
It is using a router to answer ARP requests. This will be done when the originating host believes that a destination is local, when in fact is lies beyond router.
22. Explain OSPF
It is an Internet routing protocol that scales well, can route traffic along multiple paths, and uses knowledge of an Internet's topology to make accurate routing decisions.

23. Explain Kerberos

It is an authentication service developed at the Massachusetts Institute of Technology. Kerberos uses encryption to prevent intruders from discovering passwords and gaining unauthorized access to files.

24. Explain a Multi-homed Host

It is a host that has a multiple network interfaces and that requires multiple IP addresses is called as a Multi-homed Host.

25. Explain NVT (Network Virtual Terminal)
It is a set of rules defining a very simple virtual terminal interaction. The NVT is used in the start of a Telnet session.
26. Explain Gateway-to-Gateway protocol
It is a protocol formerly used to exchange routing information between Internet core routers.

27. Explain BGP (Border Gateway Protocol)

It is a protocol used to advertise the set of networks that can be reached with in an autonomous system. BGP enables this information to be shared with the autonomous system. This is newer than EGP (Exterior Gateway Protocol).
28. Explain autonomous system
It is a collection of routers under the control of a single administrative authority and that uses a common Interior Gateway Protocol.

29. Explain EGP (Exterior Gateway Protocol)

It is the protocol the routers in neighboring autonomous systems use to identify the set of networks that can be reached
within or via each autonomous system.

30. Explain IGP (Interior Gateway Protocol)

It is any routing protocol used within an autonomous system.

31. Explain Mail Gateway

It is a system that performs a protocol translation between different electronic mail delivery protocols.

32. Explain wide-mouth frog
Wide-mouth frog is the simplest known key distribution center (KDC) authentication protocol.

33. What are Digrams and Trigrams

The most common two letter combinations are called as digrams. e.g. th, in, er, re and an. The most common three letter combinations are called as trigrams. e.g. the, ing, and, and ion.
34. Explain silly window syndrome
It is a problem that can ruin TCP performance. This problem occurs when data are passed to the sending TCP entity in large blocks, but an interactive application on the receiving side reads 1 byte at a time.
35. Explain region
When hierarchical routing is used, the routers are divided into what we call regions, with each router knowing all the details about how to route packets to destinations within its own region, but knowing nothing about the internal structure of other regions.
36. Explain multicast routing
Sending a message to a group is called multicasting, and its routing algorithm is called multicast routing.
37. Explain traffic shaping
One of the main causes of congestion is that traffic is often busy. If hosts could be made to transmit at a uniform rate, congestion would be less common. Another open loop method to help manage congestion is forcing the packet to be transmitted at a more predictable rate. This is called traffic shaping.
38. Explain packet filter
Packet filter is a standard router equipped with some extra functionality. The extra functionality allows every incoming or outgoing packet to be inspected. Packets meeting some criterion are forwarded normally. Those that fail the test are dropped.
39. Explain virtual path
Along any transmission path from a given source to a given destination, a group of virtual circuits can be grouped together into what is called path.
40. Explain virtual channel
Virtual channel is normally a connection from one source to one destination, although multicast connections are also permitted. The other name for virtual channel is virtual circuit.
41. Explain logical link control
One of two sublayers of the data link layer of OSI reference model, as defined by the IEEE 802 standard. This sublayer is responsible for maintaining the link between computers when they are sending data across the physical network connection.
42. Why should you care about the OSI Reference Model
It provides a framework for discussing network operations and design.
43. Explain the difference between routable and non- routable protocols
Routable protocols can work with a router and can be used to build large networks. Non-Routable protocols are designed to work on small, local networks and cannot be used with a router
44. Explain MAU
In token Ring , hub is called Multistation Access Unit(MAU).
45. Explain 5-4-3 rule
In a Ethernet network, between any two points on the network, there can be no more than five network segments or four repeaters, and of those five segments only three of segments can be populated.
46. Explain the difference between TFTP and FTP application layer protocols
The Trivial File Transfer Protocol (TFTP) allows a local host to obtain files from a remote host but does not provide reliability or security. It uses the fundamental packet delivery services offered by UDP.
The File Transfer Protocol (FTP) is the standard mechanism provided by TCP / IP for copying a file from one host to another. It uses the services offered by TCP and so is reliable and secure. It establishes two connections (virtual circuits) between the hosts, one for data transfer and another for control information.
47. Explain the range of addresses in the classes of internet addresses
Class A -
Class B -
Class C -
Class D -
Class E -

48. Explain the minimum and maximum length of the header in the TCP segment and IP datagram

The header should have a minimum length of 20 bytes and can have a maximum length of 60 bytes.
49. Explain difference between ARP and RARP
The address resolution protocol (ARP) is used to associate the 32 bit IP address with the 48 bit physical address, used by a host or a router to find the physical address of another host on its network by sending a ARP query packet that includes the IP address of the receiver. The reverse address resolution protocol (RARP) allows a host to discover its Internet address when it knows only its physical address.
50. Explain ICMP
ICMP is Internet Control Message Protocol, a network layer protocol of the TCP/IP suite used by hosts and gateways to send notification of datagram problems back to the sender. It uses the echo test / reply to test whether a destination is reachable and responding. It also handles both control and error messages.
51. What are the data units at different layers of the TCP / IP protocol suite
The data unit created at the application layer is called a message, at the transport layer the data unit created is called either a segment or an user datagram, at the network layer the data unit created is called the datagram, at the data link layer the datagram is encapsulated in to a frame and
finally transmitted as signals along the transmission media.

52. Explain Project 802

It is a project started by IEEE to set standards that enable intercommunication between equipment from a variety of manufacturers. It is a way for specifying functions of the physical layer, the data link layer and to some extent the network layer to allow for interconnectivity of major LAN protocols.
It consists of the following:
802.1 is an internetworking standard for compatibility of different LANs and MANs across protocols.
802.2 Logical link control (LLC) is the upper sublayer of the data link layer which is non-architecture-specific, that is remains the same for all IEEE-defined LANs.
Media access control (MAC) is the lower sublayer of the data link layer that contains some distinct modules each carrying proprietary information specific to the LAN product being used. The modules are Ethernet LAN (802.3), Token ring LAN (802.4), Token bus LAN (802.5).
802.6 is distributed queue dual bus (DQDB) designed to be used in MANs.
53. Explain Bandwidth
Every line has an upper limit and a lower limit on the frequency of signals it can carry. This limited range is called the bandwidth.
54. Difference between bit rate and baud rate.
Bit rate is the number of bits transmitted during one second whereas baud rate refers to the number of signal units per second that are required to represent those bits. baud rate = bit rate / N where N is no-of-bits represented by each signal shift.
55. Explain MAC address
The address for a device as it is identified at the Media Access Control (MAC) layer in the network architecture. MAC address is usually stored in ROM on the network adapter card and is unique.

56. Explain attenuation

The degeneration of a signal over distance on a network cable is called attenuation.

57. Explain cladding
A layer of a glass surrounding the center fiber of glass inside a fiber-optic cable.

58. Explain RAID
A method for providing fault tolerance by using multiple hard disk drives.

59. Explain NETBIOS and NETBEUI

NETBIOS is a programming interface that allows I/O requests to be sent to and received from a remote computer and it hides the networking hardware from applications. NETBEUI is NetBIOS extended user interface. A transport protocol designed by microsoft and IBM for the use on small subnets.

60. Explain redirector

Redirector is software that intercepts file or prints I/O requests and translates them into network requests. This comes under presentation layer.
61. Explain Beaconing
The process that allows a network to self-repair networks problems. The stations on the network notify the other stations on the ring when they are not receiving the transmissions. Beaconing is used in Token ring and FDDI networks.
62. Explain terminal emulation, in which layer it comes
Telnet is also called as terminal emulation. It belongs to application layer.

63. Explain frame relay, in which layer it comes

Frame relay is a packet switching technology. It will operate in the data link layer.

64. What do you meant by "triple X" in Networks

The function of PAD (Packet Assembler Disassembler) is described in a document known as X.3. The standard protocol has been defined between the terminal and the PAD, called X.28; another standard protocol exists between hte PAD and the network, called X.29. Together, these three recommendations are often called "triple X"
65. Explain SAP
Series of interface points that allow other computers to communicate with the other layers of network protocol stack.

66. Explain subnet
A generic term for section of a large networks usually separated by a bridge or router.

67. Explain Brouter
Hybrid devices that combine the features of both bridges and routers.

68. How Gateway is different from Routers

A gateway operates at the upper levels of the OSI model and translates information between two completely different network architectures or data formats.

69. What are the different type of networking / internetworking devices
Repeater: Also called a regenerator, it is an electronic device that operates only at physical layer. It receives the signal in the network before it becomes weak, regenerates the original bit pattern and puts the refreshed copy back in to the link.
Bridges: These operate both in the physical and data link layers of LANs of same type. They divide a larger network in to smaller segments. They contain logic that allow them to keep the traffic for each segment separate and thus are repeaters that relay a frame only the side of the segment containing the intended recipent and control congestion.
Routers: They relay packets among multiple interconnected networks (i.e. LANs of different type). They operate in the physical, data link and network layers. They contain software that enable them to determine which of the several possible paths is the best for a particular transmission.
They relay packets among networks that have different protocols (e.g. between a LAN and a WAN). They accept a packet formatted for one protocol and convert it to a packet formatted for another protocol before forwarding it. They operate in all seven layers of the OSI model.
70. Explain mesh network
A network in which there are multiple network links between computers to provide multiple paths for data to travel.
71. Explain passive topology
When the computers on the network simply listen and receive the signal, they are referred to as passive because they don’t amplify the signal in any way. Example for passive topology - linear bus.

72. What are the important topologies for networks

BUS topology: :in this each computer is directly connected to primary network cable in a single line.
Advantages: Inexpensive, easy to install, simple to understand, easy to extend.
STAR topology: In this all computers are connected using a central hub.
Advantages: Can be inexpensive, easy to install and reconfigure and easy to trouble shoot physical problems.
RING topology:In this all computers are connected in loop.
Advantages: ll computers have equal access to network media, installation can be simple, and signal does not degrade as much as
in other topologies because each computer regenerates it.

73. What are major types of networks and explain

Peer-to-peer network, computers can act as both servers sharing resources and as clients using the resources.
Server-based networks provide centralized control of network resources and rely on server computers to provide security and network administration

74. Explain Protocol Data Unit
The data unit in the LLC level is called the protocol data unit (PDU). The PDU contains of four fields a destination service access point (DSAP), a source service access point (SSAP), a control field and an information field. DSAP, SSAP are addresses used by the LLC to identify the protocol stacks on the receiving and sending machines that are generating and using the data. The control field specifies whether the PDU frame is a information frame (I - frame) or a supervisory frame (S - frame) or a
unnumbered frame (U - frame).
75. Explain difference between baseband and broadband transmission
In a baseband transmission, the entire bandwidth of the cable is consumed by a single signal. In broadband transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously.
76. What are the possible ways of data exchange
(i) Simplex (ii) Half-duplex (iii) Full-duplex.

77. What are the types of Transmission media

Signals are usually transmitted over some transmission media that are broadly classified in to two categories.
Guided Media:
These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic that accept
and transport signals in the form of electrical current. Optical fiber is a glass or plastic cable that accepts and transports signals in the form of light.
Unguided Media:
This is the wireless media that transport electromagnetic waves without using a physical conductor. Signals are broadcast either through air. This is done through radio communication, satellite communication and cellular telephony.
78. Explain point-to-point protocol
A communications protocol used to connect computers to remote networking services including Internet service providers.

79. What are the two types of transmission technology available
(i) Broadcast and (ii) point-to-point

80. Difference between the communication and transmission.

Transmission is a physical movement of information and concern issues like bit polarity, synchronization, clock etc. Communication means the meaning full exchange of information between two communication media.


Testing and Quality Assurance

What is Testing?
The process of exercising software to verify that it satisfies specified requirements and to detect errors.
The process of analyzing a software item to detect the differences between existing and required conditions (that is, bugs), and to evaluate the features of the software item (Ref. IEEE Std 829).
The process of operating a system or component under specified conditions, observing or recording the results, and making an evaluation of some aspect of the system or component.
What is Test Automation? It is the same as Automated Testing.

What is Acceptance Testing?
Testing conducted to enable a user/customer to determine whether to accept a software product. Normally performed to validate the software meets a set of agreed acceptance criteria.

What is Accessibility Testing?

Verifying a product is accessible to the people having disabilities (deaf, blind, mentally disabled etc.).

What is Ad Hoc Testing?
A testing phase where the tester tries to 'break' the system by randomly trying the system's functionality. Can include negative testing as well. See also Monkey Testing.

What is Agile Testing?
Testing practice for projects using agile methodologies, treating development as the customer of testing and emphasizing a test-first design paradigm. See also Test Driven Development.

What is Application Binary Interface (ABI)?
A specification defining requirements for portability of applications in binary forms across defferent system platforms and environments.

What is Application Programming Interface (API)?
A formalized set of software calls and routines that can be referenced by an application program in order to access supporting system or network services.

What is Automated Software Quality (ASQ)?
The use of software tools, such as automated testing tools, to improve software quality.

What is Automated Testing?
Testing employing software tools which execute tests without manual intervention. Can be applied in GUI, performance, API, etc. testing.
The use of software to control the execution of tests, the comparison of actual outcomes to predicted outcomes, the setting up of test preconditions, and other test control and test reporting functions.
What is Backus-Naur Form?
A metalanguage used to formally describe the syntax of a language.

What is Basic Block?
A sequence of one or more consecutive, executable statements containing no branches.

What is Basis Path Testing?
A white box test case design technique that uses the algorithmic flow of the program to design tests.

What is Basis Set?
The set of tests derived using basis path testing.

What is Baseline?
The point at which some deliverable produced during the software engineering process is put under formal change control.
What you will do during the first day of job?
What would you like to do five years from now?

Tell me about the worst boss you've ever had.

What are your greatest weaknesses?

What are your strengths?

What is a successful product?

What do you like about Windows?

What is good code?

What are basic, core, practices for a QA specialist?

What do you like about QA?

What has not worked well in your previous QA experience and what would you change?

How you will begin to improve the QA process?

What is the difference between QA and QC?

What is UML and how to use it for testing?
What is Beta Testing?

Testing of a rerelease of a software product conducted by customers.

What is Binary Portability Testing?
Testing an executable application for portability across system platforms and environments, usually for conformation to an ABI specification.

What is Black Box Testing?
Testing based on an analysis of the specification of a piece of software without reference to its internal workings. The goal is to test how well the component conforms to the published requirements for the component.

What is Bottom Up Testing?
An approach to integration testing where the lowest level components are tested first, then used to facilitate the testing of higher level components. The process is repeated until the component at the top of the hierarchy is tested.

What is Boundary Testing?
Test which focus on the boundary or limit conditions of the software being tested. (Some of these tests are stress tests).
What is Bug?
A fault in a program which causes the program to perform in an unintended or unanticipated manner.

What is Boundary Value Analysis?
BVA is similar to Equivalence Partitioning but focuses on "corner cases" or values that are usually out of range as defined by the specification. his means that if a function expects all values in range of negative 100 to positive 1000, test inputs would include negative 101 and positive 1001.

What is Branch Testing?
Testing in which all branches in the program source code are tested at least once.

What is Breadth Testing?
A test suite that exercises the full functionality of a product but does not test features in detail.

What is CAST?
Computer Aided Software Testing.
What is CMMI?
What do you like about computers?

Do you have a favourite QA book? More than one? Which ones? And why.

What is the responsibility of programmers vs QA?

What are the properties of a good requirement?

Ho to do test if we have minimal or no documentation about the product?

What are all the basic elements in a defect report?

Is an "A fast database retrieval rate" a testable requirement?

What is software quality assurance?

What is the value of a testing group? How do you justify your work and budget?

What is the role of the test group vis-à-vis documentation, tech support, and so forth?

How much interaction with users should testers have, and why?

How should you learn about problems discovered in the field, and what should you learn from those problems?

What are the roles of glass-box and black-box testing tools?

What issues come up in test automation, and how do you manage them?
What is Capture/Replay Tool?
A test tool that records test input as it is sent to the software under test. The input cases stored can then be used to reproduce the test at a later time. Most commonly applied to GUI test tools.

What is CMM?
The Capability Maturity Model for Software (CMM or SW-CMM) is a model for judging the maturity of the software processes of an organization and for identifying the key practices that are required to increase the maturity of these processes.

What is Cause Effect Graph?
A graphical representation of inputs and the associated outputs effects which can be used to design test cases.

What is Code Complete?
Phase of development where functionality is implemented in entirety; bug fixes are all that are left. All functions found in the Functional Specifications have been implemented.

What is Code Coverage?
An analysis method that determines which parts of the software have been executed (covered) by the test case suite and which parts have not been executed and therefore may require additional attention.
What is Code Inspection?
A formal testing technique where the programmer reviews source code with a group who ask questions analyzing the program logic, analyzing the code with respect to a checklist of historically common programming errors, and analyzing its compliance with coding standards.

What is Code Walkthrough?
A formal testing technique where source code is traced by a group with a small set of test cases, while the state of program variables is manually monitored, to analyze the programmer's logic and assumptions.

What is Coding?
The generation of source code.

What is Compatibility Testing?
Testing whether software is compatible with other elements of a system with which it should operate, e.g. browsers, Operating Systems, or hardware.
What is Component?
A minimal software item for which a separate specification is available.

What is Component Testing?
See the question what is Unit Testing.

What is Concurrency Testing?
Multi-user testing geared towards determining the effects of accessing the same application code, module or database records. Identifies and measures the level of locking, deadlocking and use of single-threaded code and locking semaphores.

What is Conformance Testing?
The process of testing that an implementation conforms to the specification on which it is based. Usually applied to testing conformance to a formal standard.

What is Context Driven Testing?
The context-driven school of software testing is flavor of Agile Testing that advocates continuous and creative evaluation of testing opportunities in light of the potential information revealed and the value of that information to the organization right now.

What development model should programmers and the test group use?

How do you get programmers to build testability support into their code?

What is the role of a bug tracking system?

What are the key challenges of testing?

Have you ever completely tested any part of a product? How?

Have you done exploratory or specification-driven testing?

Should every business test its software the same way?

Discuss the economics of automation and the role of metrics in testing.

Describe components of a typical test plan, such as tools for interactive products and for database products, as well as cause-and-effect graphs and data-flow diagrams.

When have you had to focus on data intergrity?

What are some of the typical bugs you encountered in your last assignment?

How do you prioritize testing tasks within a project?

How do you develop a test plan and schedule? Describe bottom-up and top-down approaches.

When should you begin test planning?

When should you begin testing?

What is Conversion Testing?
Testing of programs or procedures used to convert data from existing systems for use in replacement systems.

What is Cyclomatic Complexity?
A measure of the logical complexity of an algorithm, used in white-box testing.

What is Data Dictionary?
A database that contains definitions of all data items defined during analysis.

What is Data Flow Diagram?
A modeling notation that represents a functional decomposition of a system.

What is Data Driven Testing?
Testing in which the action of a test case is parameterized by externally defined data values, maintained as a file or spreadsheet. A common technique in Automated Testing.

What is Debugging?
The process of finding and removing the causes of software failures.

What is Defect?
Nonconformance to requirements or functional / program specification

What is Dependency Testing?
Examines an application's requirements for pre-existing software, initial states and configuration in order to maintain proper functionality.

What is Depth Testing?
A test that exercises a feature of a product in full detail.

What is Dynamic Testing?
Testing software through executing it. See also Static Testing.

What is Emulator?
A device, computer program, or system that accepts the same inputs and produces the same outputs as a given system.

What is Endurance Testing?
Checks for memory leaks or other problems that may occur with prolonged execution.

What is End-to-End testing?
Testing a complete application environment in a situation that mimics real-world use, such as interacting with a database, using network communications, or interacting with other hardware, applications, or systems if appropriate.

What is Equivalence Class?
A portion of a component's input or output domains for which the component's behaviour is assumed to be the same from the component's specification.

What is Equivalence Partitioning?
A test case design technique for a component in which test cases are designed to execute representatives from equivalence classes.

What is Exhaustive Testing?
Testing which covers all combinations of input values and preconditions for an element of the software under test.
What is Functional Decomposition?
A technique used during planning, analysis and design; creates a functional hierarchy for the software.

What is Functional Specification?
A document that describes in detail the characteristics of the product with regard to its intended features.

What is Functional Testing?
Testing the features and operational behavior of a product to ensure they correspond to its specifications.
Testing that ignores the internal mechanism of a system or component and focuses solely on the outputs generated in response to selected inputs and execution conditions.
See also What is Black Box Testing.

What is Glass Box Testing?
A synonym for White Box Testing.

Do you know of metrics that help you estimate the size of the testing effort?
How do you scope out the size of the testing effort?

How many hours a week should a tester work?

How should your staff be managed? How about your overtime?

How do you estimate staff requirements?

What do you do (with the project tasks) when the schedule fails?

How do you handle conflict with programmers?

How do you know when the product is tested well enough?

What characteristics would you seek in a candidate for test-group manager?

What do you think the role of test-group manager should be? Relative to senior management? Relative to other technical groups in the company? Relative to your staff?

How do your characteristics compare to the profile of the ideal manager that you just described?

How does your preferred work style work with the ideal test-manager role that you just described? What is different between the way you work and the role you described?

Who should you hire in a testing group and why?
What is Gorilla Testing?
Testing one particular module, functionality heavily.

What is Gray Box Testing?
A combination of Black Box and White Box testing methodologies? testing a piece of software against its specification but using some knowledge of its internal workings.

What is High Order Tests?
Black-box tests conducted once the software has been integrated.

What is Independent Test Group (ITG)?
A group of people whose primary responsibility is software testing,

What is Inspection?
A group review quality improvement process for written material. It consists of two aspects; product (document itself) improvement and process improvement (of both document production and inspection).
What is Integration Testing?
Testing of combined parts of an application to determine if they function together correctly. Usually performed after unit and functional testing. This type of testing is especially relevant to client/server and distributed systems.

What is Installation Testing?
Confirms that the application under test recovers from expected or unexpected events without loss of data or functionality. Events can include shortage of disk space, unexpected loss of communication, or power out conditions.

What is Load Testing?
See performance testing.

What is Localization Testing?
This term refers to making software specifically designed for a specific locality.

What is Loop Testing?
A white box testing technique that exercises program loops.
What is Metric?
A standard of measurement. Software metrics are the statistics describing the structure or content of a program. A metric should be a real objective measurement of something such as number of bugs per lines of code.

What is Monkey Testing?
Testing a system or an Application on the fly, i.e just few tests here and there to ensure the system or an application does not crash out.

What is Negative Testing?
Testing aimed at showing software does not work. Also known as "test to fail". See also Positive Testing.

What is Path Testing?
Testing in which all paths in the program source code are tested at least once.

What is Performance Testing?
Testing conducted to evaluate the compliance of a system or component with specified performance requirements. Often this is performed using an automated test tool to simulate large number of users. Also know as "Load Testing".

What is Positive Testing?
Testing aimed at showing software works. Also known as "test to pass". See also Negative Testing.

What is Quality Assurance?
All those planned or systematic actions necessary to provide adequate confidence that a product or service is of the type and quality needed and expected by the customer.

What is Quality audit?
A systematic and independent examination to determine whether quality activities and related results comply with planned arrangements and whether these arrangements are implemented effectively and are suitable to achieve objectives.

What is Quality Circle?
A group of individuals with related interests that meet at regular intervals to consider problems or other matters related to the quality of outputs of a process and to the correction of problems or to the improvement of quality.

What is Quality Control?
The operational techniques and the activities used to fulfill and verify requirements of quality.

What is Quality Management?
That aspect of the overall management function that determines and implements the quality policy.

What is Quality Policy?
The overall intentions and direction of an organization as regards quality as formally expressed by top management.

What is Quality System?
The organizational structure, responsibilities, procedures, processes, and resources for implementing quality management.

What is Race Condition?
A cause of concurrency problems. Multiple accesses to a shared resource, at least one of which is a write, with no mechanism used by either to moderate simultaneous access.

What is Ramp Testing?
Continuously raising an input signal until the system breaks down.

What is Recovery Testing?
Confirms that the program recovers from expected or unexpected events without loss of data or functionality. Events can include shortage of disk space, unexpected loss of communication, or power out conditions.

What is Regression Testing?
Retesting a previously tested program following modification to ensure that faults have not been introduced or uncovered as a result of the changes made.

What is Release Candidate?
A pre-release version, which contains the desired functionality of the final version, but which needs to be tested for bugs (which ideally should be removed before the final version is released).

What is Sanity Testing?
Brief test of major functional elements of a piece of software to determine if its basically operational. See also Smoke Testing.

What is Scalability Testing?
Performance testing focused on ensuring the application under test gracefully handles increases in work load.
What is the role of metrics in comparing staff performance in human resources management?
How do you estimate staff requirements?

What do you do (with the project staff) when the schedule fails?

Describe some staff conflicts youÂ’ve handled.

Why did you ever become involved in QA/testing?

What is the difference between testing and Quality Assurance?

What was a problem you had in your previous assignment (testing if possible)? How did you resolve it?

What are two of your strengths that you will bring to our QA/testing team?

What do you like most about Quality Assurance/Testing?

What do you like least about Quality Assurance/Testing?

What is the Waterfall Development Method and do you agree with all the steps?

What is the V-Model Development Method and do you agree with this model?

What is Security Testing?
Testing which confirms that the program can restrict access to authorized personnel and that the authorized personnel can access the functions available to their security level.

What is Smoke Testing?
A quick-and-dirty test that the major functions of a piece of software work. Originated in the hardware testing practice of turning on a new piece of hardware for the first time and considering it a success if it does not catch on fire.

What is Soak Testing?
Running a system at high load for a prolonged period of time. For example, running several times more transactions in an entire day (or night) than would be expected in a busy day, to identify and performance problems that appear after a large number of transactions have been executed.

What is Software Requirements Specification?
A deliverable that describes all data, functional and behavioral requirements, all constraints, and all validation requirements for software/

What is Software Testing?
A set of activities conducted with the intent of finding errors in software.

What is Static Analysis?
Analysis of a program carried out without executing the program.

What is Static Analyzer?
A tool that carries out static analysis.

What is Static Testing?
Analysis of a program carried out without executing the program.

What is Storage Testing?
Testing that verifies the program under test stores data files in the correct directories and that it reserves sufficient space to prevent unexpected termination resulting from lack of space. This is external storage as opposed to internal storage.

What is Stress Testing?
Testing conducted to evaluate a system or component at or beyond the limits of its specified requirements to determine the load under which it fails and how. Often this is performance testing using a very high level of simulated load.

What is Structural Testing?
Testing based on an analysis of internal workings and structure of a piece of software. See also White Box Testing.

What is System Testing?
Testing that attempts to discover defects that are properties of the entire system rather than of its individual components.

What is Testability?
The degree to which a system or component facilitates the establishment of test criteria and the performance of tests to determine whether those criteria have been met.

What is Test Bed?
An execution environment configured for testing. May consist of specific hardware, OS, network topology, configuration of the product under test, other application or system software, etc. The Test Plan for a project should enumerated the test beds(s) to be used.
What is Test Case?
Test Case is a commonly used term for a specific test. This is usually the smallest unit of testing. A Test Case will consist of information such as requirements testing, test steps, verification steps, prerequisites, outputs, test environment, etc.
A set of inputs, execution preconditions, and expected outcomes developed for a particular objective, such as to exercise a particular program path or to verify compliance with a specific requirement.
Test Driven Development? Testing methodology associated with Agile Programming in which every chunk of code is covered by unit tests, which must all pass all the time, in an effort to eliminate unit-level and regression bugs during development. Practitioners of TDD write a lot of tests, i.e. an equal number of lines of test code to the size of the production code.

What is Test Driver?
A program or test tool used to execute a tests. Also known as a Test Harness.

What is Test Environment?
The hardware and software environment in which tests will be run, and any other software with which the software under test interacts when under test including stubs and test drivers.

What is Test First Design?
Test-first design is one of the mandatory practices of Extreme Programming (XP).It requires that programmers do not write any production code until they have first written a unit test.
What is a "Good Tester"?

Could you tell me two things you did in your previous assignment (QA/Testing related hopefully) that you are proud of?

List 5 words that best describe your strengths.

What are two of your weaknesses?

What methodologies have you used to develop test cases?

In an application currently in production, one module of code is being modified. Is it necessary to re- test the whole application or is it enough to just test functionality associated with that module?

How do you go about going into a new organization? How do you assimilate?

Define the following and explain their usefulness:change management, Configuration Management, Version Control, and Defect Tracking.

What is ISO 9000? Have you ever been in an ISO shop?

When are you done testing?

What is the difference between a test strategy and a test plan?

What is ISO 9003? Why is it important
What is Test Harness?

A program or test tool used to execute a tests. Also known as a Test Driver.

What is Test Plan?
A document describing the scope, approach, resources, and schedule of intended testing activities. It identifies test items, the features to be tested, the testing tasks, who will do each task, and any risks requiring contingency planning. Ref IEEE Std 829.

What is Test Procedure?
A document providing detailed instructions for the execution of one or more test cases.

What is Test Script?
Commonly used to refer to the instructions for a particular test that will be carried out by an automated test tool.

What is Test Specification?
A document specifying the test approach for a software feature or combination or features and the inputs, predicted results and execution conditions for the associated tests.
What is Test Suite?
A collection of tests used to validate the behavior of a product. The scope of a Test Suite varies from organization to organization. There may be several Test Suites for a particular product for example. In most cases however a Test Suite is a high level concept, grouping together hundreds or thousands of tests related by what they are intended to test.

What is Test Tools?
Computer programs used in the testing of a system, a component of the system, or its documentation.

What is Thread Testing?
A variation of top-down testing where the progressive integration of components follows the implementation of subsets of the requirements, as opposed to the integration of components by successively lower levels.

What is Top Down Testing?
An approach to integration testing where the component at the top of the component hierarchy is tested first, with lower level components being simulated by stubs. Tested components are then used to test lower level components. The process is repeated until the lowest level components have been tested.
What is Total Quality Management?
A company commitment to develop a process that achieves high quality product and customer satisfaction.

What is Traceability Matrix?
A document showing the relationship between Test Requirements and Test Cases.

What is Usability Testing?
Testing the ease with which users can learn and use a product.

What is Use Case?
The specification of tests that are conducted from the end-user perspective. Use cases tend to focus on operating software as an end-user would conduct their day-to-day activities.

What is Unit Testing?
Testing of individual software components.
What is Validation?
The process of evaluating software at the end of the software development process to ensure compliance with software requirements. The techniques for validation is testing, inspection and reviewing
What is Verification?
The process of determining whether of not the products of a given phase of the software development cycle meet the implementation steps and can be traced to the incoming objectives established during the previous phase. The techniques for verification are testing, inspection and reviewing.
What is Volume Testing?
Testing which confirms that any values that may become large over time (such as accumulated counts, logs, and data files), can be accommodated by the program and will not cause the program to stop working or degrade its operation in any manner.

What is Walkthrough?
A review of requirements, designs or code characterized by the author of the material under review guiding the progression of the review.
What is White Box Testing?
Testing based on an analysis of internal workings and structure of a piece of software. Includes techniques such as Branch Testing and Path Testing. Also known as Structural Testing and Glass Box Testing. Contrast with Black Box Testing.

What is Workflow Testing?
Scripted end-to-end testing which duplicates specific workflows which are expected to be utilized by the end-user.
What are ISO standards? Why are they important?
What is IEEE 829? (This standard is important for Software Test Documentation-Why?)

What is IEEE? Why is it important?

Do you support automated testing? Why?

We have a testing assignment that is time-driven. Do you think automated tests are the best solution?

What is your experience with change control? Our development team has only 10 members. Do you think managing change is such a big deal for us?

Are reusable test cases a big plus of automated testing and explain why.

Can you build a good audit trail using Compuware's QACenter products. Explain why.

How important is Change Management in today's computing environments?

Do you think tools are required for managing change. Explain and please list some tools/practices which can help you managing change.

We believe in ad-hoc software processes for projects. Do you agree with this? Please explain your answer.

When is a good time for system testing?
Are regression tests required or do you feel there is a better use for resources?

Our software designers use UML for modeling applications. Based on their use cases, we would like to plan a test strategy. Do you agree with this approach or would this mean more effort for the testers.

Tell me about a difficult time you had at work and how you worked through it.

Give me an example of something you tried at work but did not work out so you had to go at things another way.

How can one file compare future dated output files from a program which has change, against the baseline run which used current date for input. The client does not want to mask dates on the output files to allow compares

Test Automation
What automating testing tools are you familiar with?
How did you use automating testing tools in your job?

Describe some problem that you had with automating testing tool.

How do you plan test automation?

Can test automation improve test effectiveness?

What is data - driven automation?

What are the main attributes of test automation?

Does automation replace manual testing?

How will you choose a tool for test automation?

How you will evaluate the tool for test automation?

What are main benefits of test automation?

What could go wrong with test automation?

How you will describe testing activities?

What testing activities you may want to automate?