BGP Multihoming!
Hello Expert,
Needed a help regarding BGP multi homing case. It seems simple at a glance yet somewhat confusing while explanation
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Hello Expert,
Needed a help regarding BGP multi homing case. It seems simple at a glance yet somewhat confusing while explanation
Categories: Uncategorized Tags:
Can’t you prepend the as path and tell BGP to send the traffic back via one specified route?
Are the AS path equal length and/or same?
Hi,
Ask your ISP if they support this because if they have policies set up using local preference at their end, no matter what you do you won’t get traffic as you desire. AS path prepend will work only if your ISP has neutral LP at their side with the other provider, which is usually not the case if the other provider is a peer.
Hello manoj,
Well we can alway control traffic outbound from our AS but we can’t control incoming traffic to our AS the reason being that Weight/Local preference come before AS-Path Med.Thus by setting weight or local preference you can always control the traffic coming out of your AS.Incoming traffic can’t be controlled due to the fact that the ISP can set its weight/local preference in such a way to override your metric/as-path settings.
I believe there are a couple of options. #1 Agree with the ISP that they will only send routes to you via a certain path, this could be done on the ISP side. Another option would be to use conditional route advertisement, i.e. to only advertise the routes to one ISP and when that ISP fails you would advertise the route to the other ISP. This is known as conditional route advertisement i.e. you will only advertise the route to the other ISP when the link to the 1st ISP fails.
Hope this helps!
Best Regards,