Route summarization is the method of summarizing routes of multiple networks/subnets to router neighbors routing table. Summarization provides advantages for example:
Saves memory – smaller routing tables reduces the memory requirements
Saves bandwidth – with less routes that need to be advertised, less data is traversed.
Saves CPU cycles – smaller routing tables means less packets need to be processed.

This is a multi-area OSPF lab, that provides an example of route summarization.

Task 1: Configure hostname of all three routers.

Router>enable
Router#configure terminal
Router(config)#hostname R1
R1(config)#no ip domain-lookup

Router>enable
Router#configure terminal
Router(config)#hostname R2
R2(config)#no ip domain-lookup

Router>enable
Router#configure terminal
Router(config)#hostname R3
R3(config)#no ip domain-lookup

Task 2: Assign IP addresses to the physical interfaces on all three routers.

R1(config)#interface ethernet 0/0
R1(config-if)#ip address 192.168.1.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface serial 1/0
R1(config-if)#ip address 100.0.25.2 255.255.255.252
R1(config-if)#no shutdown
R1(config-if)#exit


R2(config)#interface ethernet 0/0
R2(config-if)#ip address 192.168.2.1 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface serial 1/1
R2(config-if)#ip address 100.0.25.6 255.255.255.252
R2(config-if)#no shutdown
R2(config-if)#exit


R3(config)#interface serial 1/0
R3(config-if)#clock rate 8064000
R3(config-if)#ip address 100.0.25.1 255.255.255.252
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#interface serial 1/1
R3(config-if)#clock rate 8064000
R3(config-if)#ip address 100.0.25.5 255.255.255.252
R3(config-if)#no shutdown
R3(config-if)#exit

Task 3: Configure loopback addresses on Router 2. 

R2(config)#interface loopback 0
R2(config-if)#ip address 172.16.0.1 255.255.255.0
R2(config-if)#ip ospf network point-to-point
R2(config-if)#exit
R2(config)#interface loopback 1
R2(config-if)#ip address 172.16.1.1 255.255.255.0
R2(config-if)#ip ospf network point-to-point
R2(config-if)#exit
R2(config)#interface loopback 2
R2(config-if)#ip address 172.16.2.1 255.255.255.0
R2(config-if)#ip ospf network point-to-point
R2(config-if)#exit
R2(config)#interface loopback 3
R2(config-if)#ip address 172.16.3.1 255.255.255.0
R2(config-if)#ip ospf network point-to-point
R2(config-if)#exit

Task 4: Configure OSPF on all three routers. Advertise the physical and loopback interfaces for each router. Identify each router’s id with the following:
R1 = 1.1.1.1
R2 = 2.2.2.2
R3 = 3.3.3.3

R1(config)#router ospf 1
R1(config-router)#router-id 1.1.1.1
R1(config-router)#network 192.168.1.0 0.0.0.255 area 0
R1(config-router)#network 100.0.25.0 0.0.0.3 area 0
R1(config-router)#


R2(config)#router ospf 1
R2(config-router)#router-id 2.2.2.2
R2(config-router)#network 192.168.2.0 0.0.0.255 area 1
R2(config-router)#network 100.0.25.4 0.0.0.3 area 1
R2(config-router)#network 172.16.0.0 0.0.3.255 area 1
R2(config-router)#exit


R3(config)#router ospf 1
R3(config-router)#router-id 3.3.3.3
R3(config-router)#network 100.0.25.0 0.0.0.3 area 0
R3(config-router)#network 100.0.25.4 0.0.0.3 area 1

View the R1’s routing table after the OSPF process has been completed by all routers.

Task 5: Now let’s summarize what R3 shares to R1. Clear the OSPF process in order to force R3 neighbors to receive updates to the routing table learned from OSPF.

R3(config)#router ospf 1
R3(config-router)#area 1 range 172.16.0.0 255.255.252.0 
R3(config-router)#end
R3#clear ip ospf process

Finally, return back to router R1 and review the routing table, you will now see the routes summarized. The loopback interfaces routes should be seen as a single summarized route outside of area 1.

Related articles

Leave a Reply