Tag: RIP

In RIPv2 we can tune its updates there are so many ways , Lets see some of them

RIPv2 Broadcast updates

Normally RIPv2 uses 224.0.0.9 as the multicast address but we can change it to global broadcast address.

debug ip rip of R1 is given below

*Sep 25 14:38:38.069: RIP: sending v2 update to 224.0.0.9 via Serial1/1 (172.16.14.1)
*Sep 25 14:38:38.069: RIP: build update entries
*Sep 25 14:38:38.069: 10.2.2.0/24 via 0.0.0.0, metric 2, tag 0
*Sep 25 14:38:38.069: 172.16.12.0/30 via 0.0.0.0, metric 1, tag 0
*Sep 25 14:38:38.069: 172.16.23.0/30 via 0.0.0.0, metric 2, tag 0

I am going to change this
interface Serial1/1
ip rip v2-broadcast

Now RIPv2 is using 255.255.255.255 for its updates
*Sep 25 15:21:33.899: RIP: sending v2 update to 255.255.255.255 via Serial1/1 (172.16.14.1)
*Sep 25 15:21:33.899: RIP: build update entries
*Sep 25 15:21:33.899: 10.2.2.0/24 via 0.0.0.0, metric 2, tag 0
*Sep 25 15:21:33.899: 172.16.12.0/30 via 0.0.0.0, metric 1, tag 0
*Sep 25 15:21:33.899: 172.16.23.0/30 via 0.0.0.0, metric 2, tag 0

RIPv2 Unicast Updates

To change to uni cast updates follow these mentioned commands
router rip
version 2
passive-interface Serial1/0
passive-interface Serial1/1
network 172.16.0.0
neighbor 172.16.12.1
neighbor 172.16.23.1
no auto-summary

Now RIP is sending updates to those neighbors only
*Sep 25 15:26:54.423: RIP: sending v2 update to 172.16.12.1 via Serial1/0 (172.16.12.1)
*Sep 25 15:26:54.423: RIP: build update entries
*Sep 25 15:26:54.423: 10.4.4.0/24 via 0.0.0.0, metric 2, tag 0
*Sep 25 15:26:54.423: 172.16.14.0/30 via 0.0.0.0, metric 1, tag 0
*Sep 25 15:26:54.423: 172.16.34.0/30 via 0.0.0.0, metric 2, tag 0
*Sep 25 15:26:54.423: RIP: sending v2 update to 172.16.23.1 via Serial1/0 (172.16.12.1)
*Sep 25 15:26:54.423: RIP: build update entries
*Sep 25 15:26:54.423: 10.4.4.0/24 via 0.0.0.0, metric 2, tag 0
*Sep 25 15:26:54.423: 172.16.14.0/30 via 0.0.0.0, metric 1, tag 0
*Sep 25 15:26:54.423: 172.16.34.0/30 via 0.0.0.0, metric 2, tag 0
R1#
*Sep 25 15:26:54.434: RIP: ignored v2 packet from 172.16.12.1 (sourced from one of our addresses)
*Sep 25 15:26:54.738: RIP: received v2 update from 172.16.14.2 on Serial1/1
*Sep 25 15:26:54.738: 10.4.4.0/24 via 0.0.0.0 in 1 hops
*Sep 25 15:26:54.738: 172.16.23.0/30 via 0.0.0.0 in 2 hops
*Sep 25 15:26:54.738: 172.16.34.0/30 via 0.0.0.0 in 1 hops

In this article i am going to explain how to manipulate route with AD value in RIP. For this i am using the same old topology.

10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
R 10.4.4.0/24 [120/2] via 172.16.23.1, 00:00:19, Serial1/1
                        [120/2] via 172.16.12.1, 00:00:27, Serial1/0
172.16.0.0/16 is variably subnetted, 6 subnets, 2 masks
R 172.16.14.0/30 [120/1] via 172.16.12.1, 00:00:27, Serial1/0
R 172.16.34.0/30 [120/1] via 172.16.23.1, 00:00:19, Serial1/1

In here i want use R2 to reach 10.4.4.0/24 network for that i am going to use AD value manipulation.

!
access-list 1 permit 10.4.4.0
!
router rip
version 2
network 10.0.0.0
network 172.16.0.0
distance 255 172.16.23.1 0.0.0.0 1
no auto-summary

If you verify the routing table after this you can see only path .

10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
R 10.4.4.0/24 [120/2] via 172.16.12.1, 00:00:07, Serial1/0
172.16.0.0/16 is variably subnetted, 6 subnets, 2 masks
R 172.16.14.0/30 [120/1] via 172.16.12.1, 00:00:07, Serial1/0
R 172.16.34.0/30 [120/1] via 172.16.23.1, 00:00:07, Serial1/1

In this topology we are using RIPv2 and R2 is getting route information about 10.4.4.0/24 from R3 and R1. But i don’t want to install two routes in the table. I want to use R3 to reach that network for that  i am using Offset-List.

Lets check the present routing table of R2

10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
R 10.4.4.0/24 [120/2] via 172.16.23.1, 00:00:20, Serial1/1
                        [120/2] via 172.16.12.1, 00:00:28, Serial1/0
172.16.0.0/16 is variably subnetted, 6 subnets, 2 masks
R 172.16.14.0/30 [120/1] via 172.16.12.1, 00:00:28, Serial1/0
R 172.16.34.0/30 [120/1] via 172.16.23.1, 00:00:20, Serial1/1

R2#show ip route 10.4.4.0
Routing entry for 10.4.4.0/24
Known via “rip”, distance 120, metric 2
Redistributing via rip
Last update from 172.16.12.1 on Serial1/0, 00:00:00 ago
Routing Descriptor Blocks:
* 172.16.23.1, from 172.16.23.1, 00:00:20 ago, via Serial1/1
Route metric is 2, traffic share count is 1
172.16.12.1, from 172.16.12.1, 00:00:00 ago, via Serial1/0
Route metric is 2, traffic share count is 1

Offset-List Configuration
!
access-list 1 permit 10.4.4.0
!
router rip
version 2
offset-list 1 in 14 Serial1/0
network 10.0.0.0
network 172.16.0.0
no auto-summary
!

Now we can see that only one route is present in routing table

10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
R 10.4.4.0/24 [120/2] via 172.16.23.1, 00:00:07, Serial1/1
172.16.0.0/16 is variably subnetted, 6 subnets, 2 masks
R 172.16.14.0/30 [120/1] via 172.16.12.1, 00:00:09, Serial1/0
R 172.16.34.0/30 [120/1] via 172.16.23.1, 00:00:07, Serial1/1

If we debug RIP updates we can see that one route is inaccessible because of maximum hop count rule in RIP.

*Sep 21 18:06:49.248: RIP: received v2 update from 172.16.12.1 on Serial1/0
*Sep 21 18:06:49.248: 10.4.4.0/24 via 0.0.0.0 in 16 hops (inaccessible)
*Sep 21 18:06:49.248: 172.16.14.0/30 via 0.0.0.0 in 1 hops
*Sep 21 18:06:49.248: 172.16.34.0/30 via 0.0.0.0 in 2 hops