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The OSPF default mysteries

A while ago I wanted to combine the blog posts I've written about the default routes in OSPF into a single wiki article. As I started to investigate the various options you have to generate default routing in OSPF (including stub areas and not-so-stubby areas), the text quickly became too long and resulted in July IP Corner article "The OSPF default mysteries".


  1. It's always very interesting to ready your IPConer articles.
    Its so comprehensive.
    It's pity that these articles appeared only monthly :)

  2. A brilliant review of a subject which is rarely found discussed in its entirety. Nicely done!

  3. this line: The default route is originated only when a major network is matched (tested in IOS release 12.2SRC). You cannot originate a default route based on the presence of a subnet or a supernet.

    Can i not match on a network in my BGP table, to tell if BGP is up (and working)?

    i tried this:

    + ip access-list standard GOOGLE
    + permit
    + !
    + route-map GOOGLE permit 10
    + match ip address GOOGLE
    + !
    + default-information originate always metric 10 route-map GOOGLE

    and OSPF won't default-originate (though of course that network is in the table (twice!)).

  4. As I wrote (and you quoted): The default route is originated only when a major network is matched. is not a major network, is.


Constructive courteous comments are most welcome. Anonymous trolling will be removed with prejudice.