[c-nsp] bgp/ospf default route interaction

Christian Meutes christian at errxtx.net
Mon Aug 27 16:06:14 EDT 2012


On Aug 27, 2012, at 7:52 PM, Michael Ulitskiy <mulitskiy at acedsl.com> wrote:

> Now on CORE2 I add 'always' keyword to OSPF 'default-originate' command,
> making it:
> CORE2: router ospf 100 default-information originate always
> For some reason I don't understand it changes the game completely.  Now
> IBGP route is preferred over OSPF

it's because you inject the 0/0 into OSPF on CORE2 *always*, effectively
annihilating the other 0/0 advertised by CORE1s OSPF on CORE2.

Thus, the only remaining defaults are the ones learned via BGP.

Without the always-keyword it seems that the OSPF route is learned fast
enough to prevent the BGP one to be installed in.

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