Monday, December 26, 2011

Cisco RIP Authentication Configuration Example


Cisco RIP Authentication Configuration Example

We will configure RIP Authentication on Cisco routers.We will use RIP Version 2, because RIP version 1 does not support authentication.

Here is the topology for RIP Authentication configuration example:



Firstly we will configure R1 as below:

key chain AUTHENTICATION
 key 10
   key-string CISCO
!
interface Loopback0
 ip address 192.168.0.1 255.255.255.255
!
interface FastEthernet0/0
 ip address 192.168.12.1 255.255.255.0
 ip rip authentication mode md5
 ip rip authentication key-chain AUTHENTICATION
!        
interface FastEthernet0/1
 ip address 192.168.13.1 255.255.255.0
 !
router rip
 version 2
 network 192.168.0.0
 network 192.168.12.0
 network 192.168.13.0
 no auto-summary

We see that R1 ignores the updates that come from R2, because we did not configure RIP authentication on R2 yet:

R1#debug ip rip
RIP protocol debugging is on
*Mar  1 00:47:47.191: RIP: received v2 update from 192.168.13.3 on FastEthernet0/1
*Mar  1 00:47:47.195:      192.168.0.3/32 via 0.0.0.0 in 1 hops
*Mar  1 00:47:47.195:      192.168.0.4/32 via 0.0.0.0 in 2 hops
*Mar  1 00:47:47.195:      192.168.24.0/24 via 0.0.0.0 in 2 hops
*Mar  1 00:47:47.199:      192.168.34.0/24 via 0.0.0.0 in 1 hops
*Mar  1 00:47:54.951: RIP: ignored v2 packet from 192.168.12.2 (invalid authentication)

After we have done same RIP authentication on R2, then R1 accepts the RIP updates that come from R2:

R1#debug ip rip
RIP protocol debugging is on
*Mar  1 00:56:11.927: RIP: received packet with MD5 authentication
*Mar  1 00:56:11.927: RIP: received v2 update from 192.168.12.2 on FastEthernet0/0
*Mar  1 00:56:11.927:      192.168.0.2/32 via 0.0.0.0 in 1 hops
*Mar  1 00:56:11.931:      192.168.0.4/32 via 0.0.0.0 in 2 hops
*Mar  1 00:56:11.931:      192.168.24.0/24 via 0.0.0.0 in 1 hops
*Mar  1 00:56:11.935:      192.168.34.0/24 via 0.0.0.0 in 2 hops

In RIP Authentication Key chain names may be different on neighboring routers, but key-id and key-string must match.

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