Add Static Routes

[admin_2]

All:

I’m trying to create a few static routes on two Ethernet interfaces on a Cisco 2611 router (all internal - no WAN connections). Here’s an example of the situation with a router between each network.

NetA - - - - - R - - - - - NetB - - - - R - - - - - NetC - - - - - R - - - - - NetD

Route from NetA to NetD. How do I specify from NetA’s router that NetD exists?

Thanks.

[banajahm]

hi john,

i've re-drawn the diagram to make my explanation more understandable:

NetA - - - - - R1 - - - - - NetB - - - - R2- - - - - NetC - - - - - R3 - - - - - NetD

it's really quite simple. static routes work by pointing traffic destined to a network unknown to a router (R1) to another router that knows about that network.

in your case, R3 knows about NetD (i will assume that R2 doesn't know about NetD either). first, tell R2 how it can get to NetD: any packet that is destined to NetD, send it to e0 of R3.

next, tell R1: any packet that is destined to NetD, send it to e0 of R2.

now, when you ping, for example, from a PC from NetA to NetD this is what happens:

1. R1 get the packet and sees that it has to go to NetD. so, as the ip route command specifies, it will send this packet to R2's e0 interface.

2. R2 get the packet and sees that it has to go to NetD. so, it will send this packet to R3's e0 interface.

3. since R3 knows about NetD (cuz it's directly connected). the packet will be sent directly to the destination.

the command you need to use is:

ip route DEST_NETWORK DEST_MASK NEXT_HOP_IP_ADDRESS

VERY IMPORTANT: for this to work, R3 needs to know how to get to NetA. otherwise, you will be able to send traffic from NetA but you will get no replies from NetD. to solve this, perform the exact same steps but from R3's perspective.

hope i've answered your question

Cheers