[c-nsp] Central Services Topology - Design question

[Saku Ytti]

Hey,

> Question:  Have also seen comments in forum like. The best practice for this Hub and Spoke is to use TWO VRF in Hub site - "From-Spoke" and "To-Spoke"

This is immaterial implementation detail. Some shops do this, because
their automation system abstracts VRF into set of import/export
statements and clients share set and hubs share different set. Also if
you have hub and spoke in the same PE, you're going to need another
name, if not, single name is fine, but may be more difficult to
automate as name does not imply config.

ipv4 vrf hubs
  route-target export 42:hubs
  route-target import 42:spokes
ipv4 vrf spokes
  route-target export 42:spokes
  route-target import 42:hubs

Now the problem with this approach is that if you have >1 spokes in
the same PE, they are able to communicate to each other. To workaround
this, you'll need 'half duplex VRF', where ingress and egress RIB/FIB
are different.
Packets coming from spokes look at FibA, packets going to spokes look
at FibB. FibA has only route to hubs, FibA has only routes to spokes.

ip vrf spokesIn
  route-target import 42:hubs
ip vrf spokesOut
  route-target export 42:spokes
ip vrf hubs
   route-target export 42:hubs
   route-target import 42:spokes

PE1:
int Spoke1
  ip vrf forwarding spokesIn downstream spokesOut
int Spoke2
  ip vrf forwarding spokesIn downstream spokesOut
int Hub1
  ip vrf hubs
int Hub2
  ip vrf hubs


-- 
  ++ytti