Single AS multiple Dirverse Providers

Mon Jun 10 18:42:12 UTC 2013

On Jun 10, 2013, at 12:08 PM, Patrick W. Gilmore <patrick at ianai.net> wrote:

>> however, providers a/b at site1 do not send us the two /24s from
>> site b..
> 
> This is probably incorrect.
> 
> The providers are almost certainly sending you the prefixes, but your router is dropping them due to loop detection. To answer your later question, this is the definition of 'standard' as it is written into the RFC.
> 
> Use the allow-as-in style command posted later in this thread to fix your router.

I've done this many places, and find allow-as-in can be, uh, problematic. :)  Everyone says to just turn it on, but it's possible to get some strange paths in your table that way, in some circumstances.

For most users having a default route is just as good of a solution.  Each site will have a full table minus the small number of prefixes at the other site, and a static default will get packets to your upstream that has those routes.  Don't like a default?  Just static the netblocks at the other side to a particular provider.  Already have a default because you weren't taking full tables?  You're good to go, no special config needed.

Of course it depends on what your site-to-site requirements are, if they are independent islands or talking to each other with critical data all the time.

-- 
       Leo Bicknell - bicknell at ufp.org - CCIE 3440
        PGP keys at http://www.ufp.org/~bicknell/

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