Simple BGP MED lab:why traffic does not flow via Edge2?

Unanswered Question
Jul 23rd, 2009

Hi there, I have reviewed everything possible and I still can't figure out:

I shut down interface from Edge-1 to Primary ISP router. Then from Edge-1 I ping Primary router and I was expecting to see traffic flowing thru Edge-2. That does not work though. I already reviewed route-map and prefix-list and I can't understand what is wrong.

Please find attached diagram and show run for both Edge-1 and Edge-2 routers that I configured.

I have this problem too.
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news2010a Thu, 07/23/2009 - 20:14

Please ignore previous files. I fixed an issue on the route-map.

Consider these ones here. Issue still persists though.

Giuseppe Larosa Fri, 07/24/2009 - 02:01

Hello Marlon,

link between the two edges is in another FR subinterface.

What are you shutting down to emulate the fault?

and also you need to advertise the prefixes for which you want to modify MED check they are advertised on iBGP session

also you should try to ping primary on an ip address different from wan link

Hope to help


Marwan ALshawi Fri, 07/24/2009 - 03:11

i think i found it a bit strange

if you want to effect your traffic tward primary and back up why you use MED in out direction

this will effect the incoming traffic from primary and back up

for traffic to primary and back up

you couuse lcal prefrence, orign, as path in the inbound direction


news2010a Fri, 07/24/2009 - 07:32

The purpose of the exercise is:

There are e-commerce servers (network close to Edge-1 router.

For that reason Edge-1 advertises Then I want to control incoming

traffic from the ISP destined to those servers by making traffic flow thru Edge-1.

I apply the same concept for the other network and advertise it from

Edge-2, so that incoming traffic from ISP should be directed to Edge-2. To my understanding one way to control incoming traffic this way is MED. Let me know if I am missing something.

I will add the advertisement below on Edge-1 and Edge-2 and test it then.


interface Serial0/0.1 point-to-point

description Edge-1 to Edge-2

ip address

frame-relay interface-dlci 101


interface Serial0/0.2 point-to-point <==== I shutdown this for testing.

description Edge-1 to Primary

ip address


frame-relay interface-dlci 102


router bgp 123

no synchronization

bgp log-neighbor-changes

!include this

network mask <=== including this on advertisement

network mask <====including this on advertisement

network mask

neighbor remote-as 145

neighbor route-map SetMED out

neighbor remote-as 123

neighbor update-source Loopback0

no auto-summary


Marwan ALshawi Fri, 07/24/2009 - 17:48

ok in this case you are correct

you can MED, AS path or if you go a bit advanced you can use conditional advertisment

anyway good luck with your learning


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