cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
250
Views
0
Helpful
1
Replies

Multihoming to different ISPs with Private AS

mesuti
Beginner
Beginner

Is there any problem to use bgp private AS when multihoming to different ISPs and advertising the IP addresses assigned by one of the ISPs. On RFC it says that Private AS should be used only when singlehomed.

Can someone give me any explanation about the disadvantages of using Private AS in this case?

Thanks in Advance

Mesut Abdurrahmani

1 REPLY 1

wkumari
Beginner
Beginner

Well, the private AS # will not be propagated between the different ISPs. As BGPs loop detection algorithm is to watch for its own AS# in announcements, you run the risk of looping, using transit to try route between your border routers (remember, eBGP has admin distance of 20, iBGP has admin of 200), etc. This is not a good thing! (you could mitigate much of this with carefully applied route-maps that block receiving your own prefixes).

People receiving your announcements will also see inconsitent source ASs for your announcments and so you run the risk of some people not installing them.

Warren.

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: