Saturday, February 14, 2009

Watch the RIP metric when summarizing redistributed routes

I was reading through the GS archives and saw this interesting issue about the metrics of summarized routes after being redistributed into RIP.



R2 is redistributing OSPF to RIP as follows:
R2#sho run | sec router rip
router rip
version 2
redistribute ospf 1 metric 2
no auto-summary
R1 has the following route:
R1#sho ip route | sec is subnetted, 1 subnets
R [120/2] via, 00:00:11, FastEthernet0/0
1) Manual Summary
R2(config)#int f0/0
R2(config-if)#ip summary-address rip

R1#sho ip route | sec
R [120/3] via, 00:00:01, FastEthernet0/0
The metric increased by 1.

2) Auto-summary
R2(config-if)#router rip

R1#sho ip route | sec
R [120/2] via, 00:00:05, FastEthernet0/0
The metric is the same as when redistributed.


  1. hi
    one thing make sure the directly connected interfaces of R2 are always one less metric for that you need to create the offset list for the directly conneted and bind it.

    shivlu jain

  2. Hi, I really enjoy your blog. I wanted to ask you if you recommend a certain type of simulator software to practice the scenarios you have on your blog?


  3. Hi, thank you very much. I use dynagen a lot or my home lab. I usually just dig through the Groupstudy archives or the DocCD for ideas, or anything that pops in my head :)

    Good luck!

  4. really strange why it increase a metric doing manual summarization, any guess?

  5. It is kind of strange. I really can't think of a good reason for it. I found this issue in the Groupstudy archives but I didn't see a rationale behind it. I would be interested in hearing any theory about it...

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