[j-nsp] discard route resolveability in BGP path selection?

Pekka Savola pekkas at netcore.fi
Thu Feb 26 09:38:36 EST 2004


When upgrading a couple of routers to 6.1R2, we experienced a lot of
unavailability (apparently around 80 seconds) even though BGP should
have handled the situation by rerouting.  After some analysis, the
culprit may have been discard routes interfering with the BGP route
resolvability condition.  Let me elaborate:

When the iBGP peer's loopback address is removed from OSPF, the BGP
session still, more or less obviously, stays up.  But does JunOS 
implement route resolvability checks for the routes received from that 
peer? (Assuming yes, but I'd be interested in knowing which ones in 

In particular, when there exists a (default) discard route which
always matches the nexthop even if the OSPF route is removed, are the
BGP routes still considered resolveable, or are they removed from
consideration?  (draft-ietf-idr-bgp4-23.txt sect is a bit
ambiguous on that that but I assume they should be removed, but I
think they weren't.)

Thanks for clarification..

Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

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