Saturday, October 13, 2012

Static Routing In GNS3

Actually this is our first lab using GNS3. The previous post contains a few info on how to open a project and save along with configurations. In previous post, we initiated RIP on routers which computed the routing table entries automatically. Here I will add the first experiment which required manual routing table entry.

Simply open a new project and create a simple topology like shown below. (Click on any image to enlarge)

Here we have 4 routers, where routers R1 and R4 uses only one interface and R2, R3 uses two interfaces. First we need to configure each interface in use. So, after starting all the routers, we open their terminal and then configure the interfaces as we did in previous post. Configuring R1:

Configuring R2:

Configuring R3:

Configuring R4:

Now you can use show ip route command to see routing table on each table. You will see that the routing tables are incomplete. In fact, if you try to ping from R1, it wont be possible to do so. Because ping packets need a round trip route. So, in router R1, we will need to add routing table entries for network and Similarly, router R2 will only need information for network as the other two networks are directly connected to it.. R3 also only need information for network while R4 needs information for network and We will now add these information. In config mode, we can use ip route to add a routing table entry. Next screenshots shows entries for each router.

For router R1:

For router R2:

For router R3:

For router R4:

Now try to ping from each router to each interface, and it works :D Also use show ip route in routers to see the updated routing table entries we have just added. Have fun experimenting!

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