Create sub-interfaces in Linux

You can easily create sub interfaces in Linux. As root issue the following commands
linux #ifconfig eth0:1
linux # ifconfig eth0:2
This creates two subinterfaces to the eth0 device.
To make the change peramanent you have to include the settings in /etc/rc.local file in your linux machine. Otherwise these changes are lost when the system is restarted.
In RedHat/Fedora machines you can copy /etc/network-scripts/network/ifcfg-eth0 to /etc/network-scripts/network/ifcfg-eth0:1 and /etc/network-scripts/network/ifcfg-eth0:2 .
This makes changes permanent in RedHat/Fedora. In the debian machines the file to change is /etc/network/interfaces.

Zenmap - nmap frontend for Linux

Zenmap is a very good nmap gui frontend. Debian users have it in their default debian repository. To install from a debian machine give (as root or use sudo )

#aptitude install zenmap

The program was developed as a part of google summer code.

Setup network bridge in Debian and RedHat Linux

We can setup a network bridge in Debian and Redhat systems using the following methods

In RedHat Linux do the following

First install bridge-utils using yum or rpm or utility you like

Remove the ip address of the ethernet interfaces. You need a minimum of two

Then issue the following commands

#> brctl addbr br0

#> brctl addif br0 eth0
#> brctl addif br0 eth1
#> ip link set br0 up

And the bridge is ready.

To set ip address to bridge you can use

#> ip addr add 10.1.1.18/16 brd + dev br0

To configure routing on that bridge use the following command. This sets default gateway

#> route add default gw 10.1.1.1 dev br0.

In Debian use the following commands

To install bridge-utils

aptitude install bridge-utils

Then issue following commands

auto br0
iface br0 inet static
bridge_ports eth0
address 192.168.10.10
netmask 255.255.255.0
network 192.168.10.0
broadcast 192.168.10.255
gateway 192.168.10.1

To make the change permanent you have to enter these commands (except the installing command) in rc.local file in the /etc directory (Redhat ) /etc/network/interfaces ( for Debian based systems).

The brctl comes with various options inlcuding stp and others. Read manpage for details.

Use

>#man brctl