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Webcast-Catalyst9k
New Member

BGP 2 Sites /19 Routes - more specific routing?

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

4 REPLIES
Silver

Re: BGP 2 Sites /19 Routes - more specific routing?

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

New Member

Re: BGP 2 Sites /19 Routes - more specific routing?

so i can advertise my /24er routes upstream so only the nets i want will terminate on sitea and siteb?

Silver

Re: BGP 2 Sites /19 Routes - more specific routing?

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

New Member

Re: BGP 2 Sites /19 Routes - more specific routing?

Well i dont want a fallback.. it should be only static.

:-)

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