Lab 5.3.2 OSPF External Summarization

Objectives:

  • Use summarization with OSPF to reduce the number of external routes in the routing table.

Equipment Requirements:

  • Three Routers
  • One Switch with two VLANS set or two switches or two hubs
  • Two workstations

Scenario:

You have a RIP routing domain and an OSPF Area 0 with redistribution. You need to reduce the number of RIP routes that enter your OSPF Area 0. You must configure a summary-address in OSPF to only advertise one route to the RIP networks.

Step 1

Cable the lab and all interfaces as shown in the diagram. You will use loopbacks for the RIP networks.

Step 2

Configure OSPF routing on all routers.

Router-a(config)#router ospf 1
Router-a(config-router)#network 206.202.0.0 0.0.3.255 area 0

Router-b(config)#router ospf 1
Router-b(config-router)# network 206.202.0.0 0.0.3.255 area 0

Router-c(config)router ospf 1
Router-c(config-router)#network 206.202.0.0 0.0.3.255 area 0
Router-c(config-router)#router rip
Router-c(config-router)#network 192.168.1.0
Router-c(config-router)#network 192.168.2.0
Router-c(config-router)#network 192.168.3.0

Step 3

Verify that OSPF is configured correctly and all OSPF routes are listed in the routing table. On Router C the 192.168.1.0-192.168.3.0 networks should be directly connected, but not listed in the routing table of the other routers.

Step 4

On Router C add the following command to redistribute all the rip routes into your OSPF Area 0:

Router-c(config)router ospf 1
Router-c(config-router)#redistribute rip subnets

Step 5

On Router A, issue the command show ip route to see if the rip routes are being redistributed into the OSPF Area 0.

Step 6

On Router C, add the following command to properly summarize the RIP routes into the OSPF Area 0.

Router-c(config)router ospf 1
Router-c(config-router)#summary-address 192.168.0.0 255.255.252.0

Step 7

Issue the command show ip route from Router A and Router B. Record your results below.