On Thu, Oct 26, 2017 at 2:47 PM, Jason Lixfeld <jason+nanog@lixfeld.ca> wrote:
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.
blame shifting? avoiding instances where a third party filters: <ispasn> ?$ vs <ispasn> .*$ or just people's particular picadellos.