On 4/May/18 08:01, Erik Sundberg wrote:
> My questions is how do I get traffic to go directly between the PE's without
> going to the Core Routers?
>
> 1. Can I enable iBGP between the PE's in a full mesh to allow traffic between
> the PE's without going to the core's. Or does this break the Route Reflector
> model?
You could do, but then you lose the point of the RR in the first place,
as it's likely your Metro-E nodes will continue to grow, making this
iBGP mesh thing, well, messy.
> 2. Create a route policy on the Core's advertising routes learned from the
> PE's back to all the PE's on the ring.
You could do, but adds unnecessary routing complexity since the role of
an RR is to, well, reflect.
> 3. Is this one of the down sides to U Rings?
Not really a downside, just the perks of extending IP/MPLS all the way
into the Access (I drink to the death of Layer 2 Metro-E networks - my
liver will probably give out before I do, though...).
> 4. Leave it alone and move on to bigger and better things....
Now where's the fun in that :-)?
So we've solved this problem by using BGP-SD (Selective Download):
* For every prefix each Metro-E node handles, originate that toward
both RR's with NEXT_HOP=self.
* Attach a BGP community along with the routes originated toward the
RR's. For maximum saving of your precious FIB in your Metro-E nodes,
use a BGP community that is unique to the ring. This way, you don't
need to accept routes into each Metro-E's FIB that don't require the
"local" forwarding.
* Ensure the RR's reflect the routes they learn from each Metro-E node
to the other Metro-E nodes.
* Setup BGP-SD on each Metro-E node. Match the ring-specific BGP
community you added to each Metro-E node's prefix origination.
Accept those routes into FIB + default. Reject everything else (from
populating the FIB).
That should give you local forwarding within the ring, while maintaining
very sparse population of your Metro-E nodes' FIB's.
Mark.
