Re: Networks ignoring prepends?

[Tom Beecher <beecher () beecher cc>]

> Unless overridden, BGP takes -distance- into account where distance =
> AS path length.

An AS_PATH length of 10 could be a physical distance of 1 mile.

An AS_PATH length of 1 could be a physical distance of 1000 miles.

BGP TE communities exist to provide signalling in the event that the
standards implemented by a provider don't align with the desires of an ASN.
They are certainly imperfect, but they are a very useful tool in the
toolbox that can solve problems exactly as you are experiencing.

If you chose not to even attempt to use them, for whatever your reasons may
be, I guess that's all there is to say at this point.


On Tue, Jan 23, 2024 at 5:29 PM William Herrin <bill () herrin us> wrote:

> On Tue, Jan 23, 2024 at 12:34 PM Niels Bakker <niels=nanog () bakker net>
> wrote:
> > BGP, while a distance vector protocol, famously does not take
> > latency into account when making routing decisions.
>
> Unless overridden, BGP takes -distance- into account where distance =
> AS path length.
>
> Centurylink has overridden that with a localpref so that it DOES NOT
> take distance into account. Which rather defeats the function of a
> distance vector protocol.
>
> Regards,
> Bill Herrin
>
>
> --
> William Herrin
> bill () herrin us
> https://bill.herrin.us/