Tags in BGP

Unanswered Question


Let's say i have 4 routers connected. /24 and is on Router # 1 which when i advertise to Router # 2, I only want Router # 2 to advertise to Router # 3 and the rest of the networks which it learns from Router #1 sends it to other Routers or to different neighbors. My main goal is to filter the networks so it doesn't get injected into other neighbors and only sends to particular neighbors by using access-list on tags

One way of doing it is if on Router # 1, i create a

route-map set_tagging permit

set tag 5

R# 1

router bgp xxx

network mask route-map set_ tagging

Now, on Router # 2 when it learns about, depending on the access-list it forwards only to particular neighbor.

Is there any other way of filtering networks coming in without using the route-map tagging on network...Any idea, not sure if i am clear on this one or not.



I have this problem too.
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devang_etcom Thu, 03/01/2007 - 08:45

yes you can filter the network using the Prefix list, as-path accesslist, distribute list... etc...

using prefix list you can allow and deny perticular prefix from advertise to other peer or to receive the update from other peer...

but using AS-Path access-list you can allow or deny to receive route from perticular AS...



Harold Ritter Thu, 03/01/2007 - 08:54


BGP can carry community attributes that would allow you to do the same thing other routing protocols would do using tags. BGP doesn't carry tags in its updates.

You could attach a given community to a routing update on one router and filter based on that same community on another router.

Hope this helps,


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