[c-nsp] bgp/ospf default route interaction

Michael Ulitskiy mulitskiy at acedsl.com
Mon Aug 27 16:57:41 EDT 2012

Thanks for the reply.
So what you're saying is that if ospf router itself injects ospf default in its ospf database then
it would ignore any other ospf defaults it might receive (regardless of metric) and also it wouldn't 
install this default in the RIB. 
Did I get it right? 
I didn't know this rule and I'm a little surprised, but I ran a few experiments and they seem to confirm it. 


On Monday 27 August 2012 16:06:14 Christian Meutes wrote:
> Hiho,
> 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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