Creating custom network topology

Overview

Yes you read the title right , till the last you will able to create your own custom need network topology. Throughout this article we will be working on three systems let’s take example A,B and C . Now these systems will be configured in such a way that system A will be able to connect to system B and C both , but system B will only be able to connect A but not C , similarly C will be able to ping A but not B. This whole practical is performed on REHL8 linux OS.

Initially

System A

system A

System B

system B

System C

system c

Configuring new IP’s for these systems

The new ip can be set to a system by #ifconfig [n/w card name ] [new_IP]/[netmask]. Command to show the routing table #route -n

System A

New IP & routing table of system A

System B

New IP & routing table of system B

System C

New IP & routing table of system C

So basically system A has given IP192.168.1.1/30 which means that it is in the network 192.168.1.0 and /30 denotes this network is having 4 IP’s only 192.168.1.0, 192.168.1.1, 192.168.1.2 and 192.168.1.3.

System B is in the same network as A and IP assigned to it as 192.168.1.2.

Now the system C has assigned IP as 192.168.1.6/30 that means it’s network name is 192.168.1.4 as well as first IP and other three are following 192.168.1.5 , 192.168.1.6 and 192.168.1.7.

For establishing connection ,creating our own custom routing rules

The new rule can be added with the help of #route add -net command as shown:-

System A

For the system A we are adding two rules 1. to establishing connection in it’s own network and 2. for connecting system C present in other network.

new rules with routing table for system A

System B

For system B only one rule is added for connecting to system present in its own network. So that it can’t be able to connect to system C.

new rules with routing table for system B

System C

For System C two rules are added 1. to connect to system present in its own network and 2. to connect to system A . Now system C will only be able to connect to system A having IP 192.168.1.1. The genmask 255.255.255.254 denotes that only first two ip of network 192.168.1.0 will be able to connect.

new rules with routing table for system C

Final testing

System A

system A pinging to both B and C

System B

B pinging to A but not able to ping C

System C

C pinging to A but not able to ping B

Hurray!! the required network topology is successfully achieved.