BGP 2 Sites /19 Routes - more specific routing?

Unanswered Question
Jun 18th, 2008
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We have 2 sites with 7500 Routers and BGP

We own a /19 Network

Our Upstream Provider wants me now for load reduction to accept 2 times the same network on both sites.

I should then enter the "real" networks on the routers via "more specific" routes.

1 want 1 /24 network to terminate on site 1 the rest on site 2

I have no idea what my upstream provider means..



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shivlu jain Wed, 06/18/2008 - 00:09
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It's often useful to conditionally advertise some routes to upstream neighbors-

particularly if you are trying to control which link is crossed by traffic destined to a

particular network.BGP has the capability to conditionally advertise routes;

As per me you can use if the one link down automatically the /24 will be announced by the second pair. For this you can use the given command

neighbor x.x.x.x advertise-map toadvertise non-exist-map ifnotexist

access-list 10 permit

access-list 10 permit

access-list 20 deny

access-list 20 permit any

access-list 30 permit


route-map ifnotexist permit 10

match ip address 30


route-map ifnotexist deny 20


route-map toadvertise permit 10

match ip address 10



kmmehlkmmehl Wed, 06/18/2008 - 00:35
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so i can advertise my /24er routes upstream so only the nets i want will terminate on sitea and siteb?

shivlu jain Wed, 06/18/2008 - 00:44
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you can advertise the /24 by one end and with the conf given the seocnd link will chk will the first goes down then it willl be advertise bty the other end.



kmmehlkmmehl Wed, 06/18/2008 - 04:49
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Well i dont want a fallback.. it should be only static.



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