From: Stylen (globalfx@xxxxxxxxxxxxxx)
Date: Fri Sep 29 2000 - 23:26:24 GMT-3
Yes, BGP will look for the route in its routing table, if it goes away, then
the routes in the advertise list will be advertised via eBGP. this is used
for backing up a link, i.e. if you have two routers connected to to a
external network. You might only want one of them advertising a specific
route, perhaps because of location, but if the link between that router and
the external network goes down, then the second router will begin
advertising the route for redundancy. if you have the second router watch
for the link between the first router and the external network in its
routing table, when the route goes dissappears, then it knows to advertise
the route designated by advertise-map.
Internet
| |
| |204.0.0.4/30
R1------R2
|
|
204.2.3.0/24
the 204.0.0.5 route will be in R1's routing table, via a IGP. when the link
between R2 and the internet goes down, then the 204.0.0.5 route will
dissappear from the routing table in R1 then R1 will advertise the route to
204.2.3.0/24 to the internet. When the 204.0.0.4/30 route comes back up, R1
will stop advertising 204.2.3.0/24, and R2 will take over.
Richard Foltz, CCNP, CCNP-Voice, CCDP, MCSE+I, Network+, A+
Technical Solutions Consultant
Sprint ENS
-----Original Message-----
From: abdul_rahim@ccsi.canon.com <abdul_rahim@ccsi.canon.com>
To: ccielab@groupstudy.com <ccielab@groupstudy.com>
Date: Friday, September 29, 2000 7:58 PM
Subject: Conditional BGP Advertisements
>The following statement as described on cisco in BGP routing process
>neighbor a.b.c.d advertise-map <route-map 1> no-exist-map <route-map 2>
>
>
>Advertises the routes specified in route-map1 when it finds that the routes
>specified in route-map 2 does not exists any more in the BGP table
>And they call it as Conditional Advertisement
>
>My question is that the routes in route-map1 ,do they have to be present in
>the BGP table,
>I am not getting the point at all
>
>Can some body explain it to all of the group in a bit detail or redirect to
>a certain URL ,I do have the URL on cisco sit
>http://cisco.com/warp/public/459/34.html
>
>Any feedbacks would be highly appreciated
>Thanks
>Abdul
>
>
>
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