[c-nsp] BGP Route Reflector Case

[adamv0025 at netconsultings.com]

Hi Curtis,

> Curtis Piehler
> Sent: Thursday, February 23, 2017 4:50 AM
> 
> This is more of a design question but looking to implement on IOS-XR if
it's
> possible.  Can a router act as a dual purpose route reflector?  What I
mean by
> that, can it serve the purpose of both a local market route reflector and
> regional route reflector?  Basically having to peer a bunch of local
market
> route reflectors does not scale hence the need for a regional or 2nd level
> route reflectors at the top.  Local market route reflectors do solve the
issue
> of sub-optimal routing from a local market perspective.

I don't like the idea, as Gert mentioned it's going to delay the
convergence, I tried it once and it's a mess. 


If you are running MPLS L3VPNs in your backbone, then using Type1 RDs would
allow you to get all paths to all routers taking care of sub-optimal path
reflection (basically same effect as full mesh) and you could reduce your
complicated RR infrastructure into a single cluster (if you need to you can
scale the amount of paths by careful selection of RDs). 

If you are running pure IP backbone, then you can use add-path to advertise
all or a subset of paths. 

When advertising all paths you may end up with lots of paths per prefix,
which translates into increased memory consumption. 
But when advertising only a subset of paths you are at the mercy of RRs
doing the best path selection on behalf of Clients, 
That's where ORR comes to play, the documentation to the feature is
nonexistent and I'm not even sure it's available in a non-vXR code?  
-but it allows RR to advertise only relevant primary and backup path to
clients using ADD-PATH.  
This is the best config description so far: 
https://supportforums.cisco.com/discussion/13207456/xrv-9k-bgp-orr-does-not-
work


adam

netconsultings.com
::carrier-class solutions for the telecommunications industry::