Generating a default route in RIP – Redistribution of static route

Table of Contents

1

Generating a default route in RIP.

There are several ways to generate a default route (0.0.0.0/0) as a RIP route and advertise it to other routers, as follows

Redistribute static default route to RIP
default-information originate command
ip default-network command

The ip default-network command does not advertise the default route 0.0.0.0/0 itself, but it allows it to play the same role as the default route.

In the following sections, we will explain a simple configuration example of redistributing the default route of a static route to RIP.

Redistribute static default route to RIP

Network diagram

図 RIPでのデフォルトルート生成の設定例ネットワーク構成 — Figure Network Diagram

Condition

Allow R2 to advertise the default route to R3 with RIP to ensure connectivity for all interfaces.
The default route generation is done by static route redistribution.

Initial Configuration

R1

interface Loopback0
 ip address 172.16.2.1 255.255.255.0 secondary
 ip address 172.16.1.1 255.255.255.0
!
interface Ethernet0/0
 ip address 192.168.12.1 255.255.255.0
!
ip route 192.168.0.0 255.255.0.0 192.168.12.2

R2

interface Ethernet0/0
 ip address 192.168.12.2 255.255.255.0
!
interface Ethernet0/1
 ip address 192.168.23.2 255.255.255.0
!
router rip
 version 2
 network 192.168.23.0
 no auto-summary

R3

interface Loopback0
 ip address 192.168.3.3 255.255.255.0
!
interface Ethernet0/0
 ip address 192.168.23.3 255.255.255.0
!
router rip
 version 2
 network 192.168.3.0
 network 192.168.23.0
 no auto-summary

Step1: Configure static default route

Configure the default route as a static route on R2.

R2

ip route 0.0.0.0 0.0.0.0 192.168.12.1

Step2: Redistribute static routes to RIP

Redistribute the static route to RIP on R2 in order to make the default route as a RIP route.

R2

router rip
 redistribute static

When the redistribution source is static and connected, there is no need to specify a seed metric.

Step3: Verify default route

Verify that the default route is registered as a RIP route in the routing table on R3.

R3

R3#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is 192.168.23.2 to network 0.0.0.0

C    192.168.23.0/24 is directly connected, Ethernet0/0
C    192.168.3.0/24 is directly connected, Loopback0
R*   0.0.0.0/0 [120/1] via 192.168.23.2, 00:00:26, Ethernet0/0

Step4: Verify Communication

Execute ping from R3 to R1 to verify that communication is possible. Since there is a default route, the ping response will be returned successfully.

R3

R3#ping 172.16.1.1 source 192.168.3.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds:
Packet sent with a source address of 192.168.3.3
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/12/20 ms
R3#ping 172.16.2.1 source 192.168.3.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.2.1, timeout is 2 seconds:
Packet sent with a source address of 192.168.3.3
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/10/20 ms