GNS3 network topology config

Topology:

Now I am showing you how to create a simple topology. Drag one more router to work board and then start. Clicks on add a link option and then choose manual.
  Right click on R1 and select f0/0 (interface to connect to R2) and then click on R2 and select interface.
 Use following sample config to check connectivity.

on Router 1

R1#
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#int
R1(config)#interface fas
R1(config)#interface fastEthernet 0/0
R1(config-if)#no shut

 R1(config-if)#
*Mar 1 00:38:10.207: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up
*Mar 1 00:38:11.207: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up
R1(config-if)#ip add
R1(config-if)#ip address 192.168.0.1 255.255.255.0
R1(config-if)#

on Router 2

R2#conf
R2#configure t
Enter configuration commands, one per line. End with CNTL/Z.
R2(config)#int
R2(config)#interface fas
R2(config)#interface fastEthernet 0/0
R2(config-if)#no shut
R2(config-if)#ip add
*Mar 1 00:14:26.703: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up
*Mar 1 00:14:27.703: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up
R2(config-if)#ip add
R2(config-if)#ip address 192.168.0.2 255.255.255.0
R2(config-if)#exit
R2(config)#exit
R2#
*Mar 1 00:14:41.231: %SYS-5-CONFIG_I: Configured from console by console
R2#ping 192.168.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.1, timeout is 2 seconds:
.!!!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 20/29/48 ms
R2#

Virtual PC:

Now I show you how to add PC to complete the topology. The Virtual PC Simulator is a program that runs within Windows or Linux. It has limited functionality, but most important, it allows pings and traceroutes. These are the most common testing commands used during CCNA or CCNP training and are often the only commands needed. Using VPCS you will save memory and CPU cycles. If you do not need more functionality in a workstation within your topology, I highly recommend VPCS. The Virtual PC Simulator is a free product

open VPCS and it is best to open the Virtual PC Simulator before starting GNS3.
For help, just type? at the prompt. VPCS supports up to nine PCs. Just type a number to switch to another PC. Use the Show command to view a PC’s IP or MAC address. To assign an IP address, subnet mask, and default gateway to a PC, follows this format at the prompt.
ip 192.168.1.1 192.168.1.254 24
The above command assigns the PC an IP address of 192.168.1.1 with a /24 subnet mask and a default gateway of 192.168.1.254. To switch to PC2, just type a 2 and press Enter and assign connectivity settings to PC2:
ip 192.168.2.1 192.168.2.254 24
Now go to GNS3 and drag host on to work board.
  Right click C1 and choose configure. Then go to NIO UDP.
  Local port: 30000
Remote host: 127.0.0.1
Remote port: 20000
These settings correspond to VPCS 1. Click the Add button and then OK.
Assign the following settings to C2 in the same way as C1:
Local port: 30001
Remote host: 127.0.0.1
Remote port: 20001
To keep topology simple I am using one router & two host, I have given following config to router and tested connected between hosts.
  R1#
R1#conf
R1#configure t
R1(config)#int fastEthernet 0/0
R1(config-if)#ip add 192.168.1.254 255.255.255.0
R1(config-if)#no shut
R1(config-if)#exit
R1(config)#int fastEthernet 0/1
R1(config-if)#ip address 192.168.2.254 255.255.255.0
R1(config-if)#no shut
R1(config-if)#
And then tested on VPCS prompted.

Enjoy and let me know if you are feeling any difficulty, remember Google is our best friend. Any query doesn’t hesitate to contact.

Usefull links for learn more.