ospf and manual summarization of routes

[sarahr202]

Hi every body!

Please consider the following routing table of a router running ospf

c 172.172.1.0/24 directly connected loop1

c 172.172.2.0/24 directly connected loop2

c 172.172.3.0/24 directly connected loop3

( i just loop 1 means loopback 1 and so forth)

Now if i want to summarize these connected routes. which command i have to use? should i use the same command to summarize these routes had they been learned by ospf?

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Consider the following routing table of a router running ospf

0ex 172.172.1.0 via 192.192.192.1 s1

0ex 172.172.2 .0 via 193.193.193.2 s2

These routes are redistributed, which command can i use to summarize these routes?

Thanks a lot!

[Giuseppe Larosa · Accepted solution]

Hello Sarah,

subnets advertised by network commands can be summarized only at area boundary by an ABR and so this requires a multi-area OSPF domain.

the command is

router ospf 10

area x range 172.172.0.0 255.255.252.0

if instead the prefixes are redistributed into OSPF only the ASBR that is injecting the prefixes in OSPF can aggregate them

router ospf 10

redistribute connected subnets

summary-address 172.172.0.0 255.255.252.0

the result will be

O Ex 172.172.0.0/22

Hope to help

Giuseppe