Configuring RIP Default Information Originate in Cisco

Pre-requisites: RIP, Configuring RIP Versions 1 and 2 in Cisco.

After configuring one or multiple default routes on the routers in the routing protocol’s domain, the routing protocol (in our case Routing Information Protocol) can advertise default routes, and each router chooses the best default route to list as that router’s gateway of last resort.

RIP has built-in features which allow the router on which RIP is configured to originate and propagate a default route to its direct neighbors which will propagate throughout the entire RIP routing domain. RIP supports three out of four methods to configure default route propagation which is as follows: 

Method	Supported by RIP or not
Configuring static route to 0.0.0.0 with the redistribute static command	YES
Using the default information originate command	YES
Using ip default-network command	YES
Using summary routes	NO

Configuring RIP Default Information to Originate:

Step 1: Create the 4 router topologies in GNS3 as shown in the image below:

Step 2: Configure the IPv4 address on the physical interface of the routers:

On R1:

R1(config)#int f0/0
R1(config-if)#ip address 12.0.0.1 255.255.255.0
R1(config-if)#no shutdown

On R2: 

R2(config)#int f0/0
R2(config-if)#ip address 12.0.0.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#int f1/0
R2(config-if)#ip address 23.0.0.1 255.255.255.0
R2(config-if)#no shutdown

On R3:

R3(config)#int f1/0
R3(config-if)#ip address 23.0.0.2 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#int f0/0
R3(config-if)#ip address 34.0.0.1 255.255.255.0
R3(config-if)#no shutdown

On R4:

R4(config)#int f0/0
R4(config-if)#ip address 34.0.0.2 255.255.255.0
R4(config-if)#no shutdown

Step 3: Enabling RIP on all routers using the router rip global configuration command :

R1(config)#router rip 
R1(config-router)#network 12.0.0.0

R2(config)#router rip 
R2(config-router)#network 12.0.0.0
R2(config-router)#network 23.0.0.0

R3(config)#router rip
R3(config-router)#network 23.0.0.0
R3(config-router)#network 34.0.0.0

R4(config)#router rip 
R4(config-router)#network 34.0.0.0

Step 4: Checking the IPv4 routing table on the routers for RIP route entry :

R1#show ip route

R2#show ip route

R3#show ip route

R4#show ip route

Step 5:  Configuring R1 to always originate and propagate a default route throughout the RIP routing domain:

R1(config)#router rip
R1(config-router)#default-
information originate

Step 6: Verifying whether the default route is being propagated correctly by R1 or not by viewing the routing table of R2, R3, and R4 and looking for the entry of default route and gateway of last resort:

R2#show ip route

R3#show ip route

R4#show ip route

Step 7: Checking RIP database on all the routers:

R1#show ip rip database

R2#show ip rip database

R3#show ip rip database

R4#show ip rip database

Checking Connectivity:

Capturing Interface in GNS3 Using Wireshark:

To capture the interface in GNS3 :

1. Make sure that Wireshark is installed on your PC.
2. Hover over the interface you want to capture and right-click on the interface  
3. A drop-down menu will appear with some options.
4. Select the option that says “Start capture”.

RIP Advertisements :

Packets highlighted in red are RIPv1 advertisements:

RIPv1 advertisement (request message) packet format :