Single AS multiple Dirverse Providers

Mon Jun 10 16:58:09 UTC 2013

On Mon, Jun 10, 2013 at 9:43 AM, Joe Abley <jabley at hopcount.ca> wrote:

>
> On 2013-06-10, at 18:36, "Dennis Burgess" <dmburgess at linktechs.net> wrote:
>
> > I have a network that has three peers, two are at one site and the third
> > is geographically diverse, and there is NO connection between the two
> > separate networks.
> >
> > Currently we are announcing several /24s out one network and other /24s
> > out the second network, they do not overlap.  To the internet this works
> > fine, however, providers a/b at site1 do not send us the two /24s from
> > site b..   We have requested them to, but have not seen them come in,
> > nor do we have any filters that would prohibit them from coming in.
> >
> > Is this normal?
>
> Yeah.
>
> > Can we receive those routes even though they are from
> > our own AS?
>
> You can stop them from being suppressed inbound by using "neigh x.x.x.x
> allowas-in" on a cisco, or "set neigh x.x.x.x allowas-in" on JunOS.
>
> > What is the "best practice" in this case?
>
> I don't know. Above seems reasonable. I've seen people join their sites
> with tunnels plumbed to router loopbacks in different sites and run IGPs
> over them before; this gives them inter-site connectivity which makes the
> question moot. But it involves tunnels.
>
>
> Joe
>
>
>
If your upstream provider runs JunOS, they may not be aware
that their gear won't send you the routes by default, no matter
what their policy says:

"The JUNOS software does not advertise the routes learned from one external
BGP (EBGP) peer back to the same EBGP peer. In addition, the software does
not advertise those routes back to any EBGP peers that are in the same AS
as the originating peer, regardless of the routing instance. You can modify
this behavior by including the advertise-peer-as statement in the
configuration."
(from
http://www.juniper.net/techpubs/software/junos/junos95/swconfig-routing/id-13225234.html#id-13255463

So, you may need to help walk them through adding the "advertise-peer-as"
flag to your neighbor configurations if they use Juniper kit.

Matt