What's the point of prepend communities?

Jason Lixfeld jason+nanog at lixfeld.ca
Thu Oct 26 18:47:44 CST 2017


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.



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