VRF routing process limitations

A while ago, Cisco IOS did not allow you to run more than 30 routing processes per router, significantly limiting the options of Service Providers who wanted to support OSPF as the PE-CE routing protocol. The architectural reason for the limit is a 32-bit mask that’s used in Cisco IOS to mark individual routing protocols. The routing protocol ID (as displayed by the show ip protocol summary command) is thus limited to values 0 to 31. With value 0 being reserved for connected routes and value 1 for static routes, 30 values are left to number the routing protocols.

Later IOS releases removed the limitation by allowing the same routing protocol ID to be used for different routing protocols in different VRFs. While this solution satisfies the needs of most customers, it also causes interesting side effects.

Read more in the VRF routing process limitations article in the CT3 wiki.

7 comments:

  1. Hi Ivan,

    You mistakely wrote "router bgp" in the line describing RIP..

    Good Post!

    ReplyDelete
  2. Fixed. Thanks for the feedback!

    ReplyDelete
  3. please i want some one who can tell where is labs configuration ........



    thanks

    ReplyDelete
  4. What lab configuration?

    ReplyDelete
  5. Howdy Ivan,

    you refer to
    "Later IOS releases removed the limitation by allowing the same routing protocol ID to be used for different routing protocols in different VRFs."

    What IOS version corrects this limitation and for what platforms?

    Thanks

    ReplyDelete
  6. http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gtospfvf.pdf

    ReplyDelete
  7. Ivan,

    Super, thanks.

    V/R

    Sparky

    ReplyDelete

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Ivan Pepelnjak, CCIE#1354, is the chief technology advisor for NIL Data Communications. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.