RIP unicast Updates

Lessons Learned:

RIP Unicast updates – one reason you might want to use unicast updates is to make sure the other devices on the specific segment would not be able to receive routing control plane updates.

 Using unicast updates – when the packets transit over the layer 2 switch,  which normally switches the packets based on the unicast CAM table. This means that the RIP updates will not be replicated to any other ports on the LAN.

Technically this could be considered a security feature of the routing protocol – not using multicast of broadcasts. Instead only define the unicast neighbors of where you want to multicast neighbors of where you want the updated to be sent.

The disadvantage is that we would need to keep track of all the routers that are running the protocol.

Configurations / implementations of Unicasts

On router 1:

R1(config)#router rip

R1(config-router)#neighbor 192.168.1.3

R1(config-router)#passive-interface fastEthernet 0/0

Note: the passive interface command will stop the broadcast or multicast updates but still allow the unicast updates.

R1#sh run | s router rip

router rip

version 2
passive-interface FastEthernet0/0
network 192.168.1.0
neighbor 192.168.1.3
no auto-summary

R1#

---------------------------------------------------------------------

R1#sh run | s router rip

router rip

 version 2

 passive-interface FastEthernet0/0

 network 192.168.1.0

 neighbor 192.168.1.1

 no auto-summary

R1#

*Mar  1 00:27:14.807: RIP: sending v2 update to 192.168.1.3 via FastEthernet0/0 (192.168.1.1)

*Mar  1 00:27:14.807: RIP: build update entries - suppressing null update

Note:  We now see the updates going to the unicast IP address and not the broadcast or multicast address.