nanog mailing list archives

Re: Service Providers behaviour for dual homed enterprises


From: Mark Tinka <mark.tinka () seacom mu>
Date: Thu, 24 Sep 2015 15:47:24 +0200



On 24/Sep/15 15:21, William Herrin wrote:
Hi Jason,

That's normal. Verizon does it too. Both have "community" tags which
you can attach to your route advertisement. Each will have one that
indicates they should give external routes the same "local pref" as
the route you announce to them. Tagging your route announcement with
the proper community will cause them to route based on AS path length
as you expect.

Depending on the provider, this can't always be guaranteed, i.e., that
the available LOCAL_PREF values a customer can trigger via a BGP
community support anything <= what routes the network considers "external".

What's possible (or available) may also be influenced by whether one's
upstream is "transit-free" or not, I imagine.

Mark.


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