BGP 2 Sites /19 Routes - more specific routing?

Unanswered Question
Jun 18th, 2008

Hello!

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 1.2.3.4/19 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..

http://www.cisco.com/en/US/docs/ios/12_0/np1/configuration/guide/1cbgp.html#wp8238

thanks!

marco

I have this problem too.
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shivlu jain Wed, 06/18/2008 - 00:09

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 172.28.23.0 0.0.0.255

access-list 10 permit 172.28.23.0 0.0.0.255

access-list 20 deny 10.1.3.0 0.0.0.255

access-list 20 permit any

access-list 30 permit 10.1.3.0 0.0.0.255

….

route-map ifnotexist permit 10

match ip address 30

!

route-map ifnotexist deny 20

!

route-map toadvertise permit 10

match ip address 10

regards

shivlu

kmmehlkmmehl Wed, 06/18/2008 - 00:35

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

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.

regards

shivlu

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