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What's the point of prepend communities?
- Subject: What's the point of prepend communities?
- From: jason+nanog at lixfeld.ca (Jason Lixfeld)
- Date: Thu, 26 Oct 2017 14:47:44 -0400
- In-reply-to: <CAP-guGVLHrvhoqGZ8c3fZ5wO-zJyagx6WQhRPJ=5H=p=VKqh2Q@mail.gmail.com>
- References: <[email protected]> <CAP-guGVLHrvhoqGZ8c3fZ5wO-zJyagx6WQhRPJ=5H=p=VKqh2Q@mail.gmail.com>
Hi Bill,
> On Oct 26, 2017, at 2:37 PM, William Herrin <bill at 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.