OSPF route summarization

we still use same network setup from the previous lab but with a little modification

*there's a bit error on the image, L81-84 actually on R5

add 4 new loopbacks

• on R5, advertise inside area 40

interface Loopback81

 ip address 81.1.1.1 255.0.0.0

!

interface Loopback82

 ip address 82.1.1.1 255.0.0.0

!

interface Loopback83

 ip address 83.1.1.1 255.0.0.0

!

interface Loopback84

 ip address 84.1.1.1 255.0.0.0

!

interface Loopback85

 ip address 85.1.1.1 255.255.255.0

router ospf 1

 log-adjacency-changes

..

 network 82.0.0.0 0.255.255.255 area 40

 network 83.0.0.0 0.255.255.255 area 40

 network 84.0.0.0 0.255.255.255 area 40

 network 85.1.1.0 0.0.0.255 area 40

• on R4, advertise into RIP

interface Loopback99

 ip address 99.1.1.1 255.0.0.0

!

interface Loopback100

 ip address 100.1.1.1 255.0.0.0

!

interface Loopback101

 ip address 101.1.1.1 255.0.0.0

!

interface Loopback102

 ip address 102.1.1.1 255.0.0.0

router rip
 version 2
..
 network 99.0.0.0
 network 100.0.0.0
 network 101.0.0.0
 network 102.0.0.0
 network 192.168.1.0
 no auto-summary

there are two type of summarization perform by OSPF

• for inter area route (area range command)
• for external route (summary-address command at ASBR)

now that we've add all the new loopbacks, all router should learn all the new network already

R3 routing table

R3>sh ip rou

..

O E2 102.0.0.0/8 [110/20] via 172.16.3.2, 00:10:26, Serial0/0

O E2 100.0.0.0/8 [110/20] via 172.16.3.2, 00:10:26, Serial0/0

O E2 101.0.0.0/8 [110/20] via 172.16.3.2, 00:10:26, Serial0/0

O E2 99.0.0.0/8 [110/20] via 172.16.3.2, 00:10:27, Serial0/0

..

R4 routing table

R4#sh ip rou

..

     84.0.0.0/32 is subnetted, 1 subnets

     81.0.0.0/32 is subnetted, 1 subnets

     83.0.0.0/32 is subnetted, 1 subnets

     82.0.0.0/32 is subnetted, 1 subnets

..

• let's do the inter area summary routing first

on R3

R3(config)#router os 1

R3(config-router)#area 40 range 80.0.0.0 248.0.0.0

now routing table on other routers should show summary route only

O IA 80.0.0.0/5 [110/130] via 172.16.2.2, 00:02:32, Serial0/0

• now we'll configure external summary address, do this on ASBR to summarize route from R4

on R1

R1(config)#router os 1

R1(config-router)#summary-address 100.0.0.0 248.0.0.0

now routing table on other routers should show summary route only

O E2 96.0.0.0/5 [110/20] via 172.16.2.2, 00:00:07, Serial0/0

happy routing ;)