nanog mailing list archives

Re: What's the point of prepend communities?


From: Jason Lixfeld <jason+nanog () lixfeld ca>
Date: Thu, 26 Oct 2017 14:47:44 -0400

Hi Bill,

On Oct 26, 2017, at 2:37 PM, William Herrin <bill () herrin us> wrote:

BGP routing is based on "distance". Distance in BGP is primarily calculated as the number of ASNs in the AS Path. 
Prepends make a path more distance, encouraging routers to choose a different path if one is available.

I understand how prepends fit in the context of best path selection, but my question was more the difference between a 
customer signalling the ISP to prepend their AS using a BGP community stamped to a prefix vs. the customer prepending 
their own AS instead.


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