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.

Scenario:

R1---RIP---R2---OSPF---R5---5.5.5.5/32

R2 is redistributing OSPF to RIP as follows:
R2#sho run | sec router rip
router rip
 version 2
 redistribute ospf 1 metric 2
 network 192.168.0.0
 no auto-summary
R1 has the following route:
R1#sho ip route | sec 5.0.0.0
     5.0.0.0/32 is subnetted, 1 subnets
R       5.5.5.5 [120/2] via 192.168.0.2, 00:00:11, FastEthernet0/0
1) Manual Summary
R2(config)#int f0/0
R2(config-if)#ip summary-address rip 5.0.0.0 255.0.0.0 

R1#sho ip route | sec 5.0.0.0
R    5.0.0.0/8 [120/3] via 192.168.0.2, 00:00:01, FastEthernet0/0
The metric increased by 1.

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

R1#sho ip route | sec 5.0.0.0
R    5.0.0.0/8 [120/2] via 192.168.0.2, 00:00:05, FastEthernet0/0
The metric is the same as when redistributed.
posted by deadhead blues at 11:34 PM
Labels: , ,

6 comments:

  1. AnonymousFebruary 16, 2009 at 8:30 AM

    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.

    regards
    shivlu jain

    ReplyDelete
  2. AnonymousFebruary 16, 2009 at 11:06 AM

    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?

    Thanks!

    ReplyDelete
  3. deadhead bluesFebruary 16, 2009 at 12:02 PM

    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 :)

    http://www.groupstudy.com/archives/ccielab/

    Good luck!

    ReplyDelete
  4. AnonymousFebruary 20, 2009 at 5:45 PM

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

    ReplyDelete
  5. deadhead bluesFebruary 20, 2009 at 6:00 PM

    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...

    ReplyDelete
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    ReplyDelete

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