Re: BGP - Preventing the AS from advertising local net

Try using the neighbor x.x.x.x prefix-list command. That should allow you
to filter out just the /24 as long as your prefix-list is written
correctly.

Also, you may be confusing the no-advertise and no-export
communities....which I don't think you need to solve that problem anyway.
 

From:
ccie_ka_at_gmx.de
To:
ccielab_at_groupstudy.com
Date:
04/03/2010 10:44 AM
Subject:
BGP - Preventing the AS from advertising local net
Sent by:
nobody_at_groupstudy.com

Hi GS,

assume there is one AS with the network 172.16.0.0/24
Also there are 2 other AS's

What is the best practice to prevent _only_ this network to advertise to
the BB routers ?

router bgp 33
 neighbor x.x.x.x remote-as 33
 neighbor x.x.x.x send-community both
 neighbor x.x.x.x route-map PREV out

ip prefix-list prevent seq 5 172.16.0.0/24

route-map PREV
 match ip address prefix-list prevent
 set community no-advertise

THis soulution prevent the local net to send to the neighbor..

Right now my problem is I doesn't understand why...;-)
Because I thought the community no-advertise is send to the _next_ AS and
prevent the specific prefix to send outr the neighbor AS ?!?!

Please can anyone explain me if this a normal behaviour...

Thanks

Dennis

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