summary-address with route flapping using bgp?

[ishrak_khan]

there is a case study at cisco site for various types of configuration using BGP, in this i find a topic interesting and that is using route flapping

when we use summary-address then the BGP update will not reflect the perticular link,if it is down.

this is might be a vauge question as i am not giving details as i am new to this subject

now the question is "can i use the route flapping so that i can view the address of the link that is down?" if yes then plz give me an example

[Georg Pauwen]

Hello,

when you use the aggregate address with the summary-only option, if a more specific route other than the actual aggregate flaps, this cannot be viewed by consulting the flap statistics. The reason is that the router where bgp dampening is configured never receives the more specific route, as it is already suppressed by the originating router. Here is an example:

Router R1 originates the following networks and uses the aggregate address with the summary-only option:

router bgp 1

aggregate-address 192.168.0.0.255.255.0.0 summary-only

network 192.168.1.0 mask 255.255.255.0

network 192.168.2.0 mask 255.255.255.0

network 192.168.3.0 mask 255.255.255.0

neighbor 2.2.2.2 remote-as 2

neighbor 2.2.2.2 ebgp-multihop

neighbor 2.2.2.2 update-source loopback0

Router R2 would only receive the aggregate route. If e.g. 192.168.1.0 flaps, R2 would not notice that route flapping, since it is not in its BGP table...

Does that answer your question ?

Regards,

Georg