MPLS design question

Colin Higgins · ‎12-08-2016

Forgive me if this is a bit complex, but I am not sure how to proceed here.

I want to take the routing/subnet information from multiple VRFs (routing tables) that are currently in their own OSPF instances, and send them across a BGP/MPLS network.

I would have a Catalyst 3850 switch with the VRFs and OSPF instances defined on it, and this would route to the upstream ASR router that would perform BGP/MPLS.

switch---->router---MPLS----router---->switch

So let's say the switch has the following configured

ip vrf RED
rd 100:1
!
ip vrf BLUE
rd 200:1

interface Vlan71
ip vrf forwarding RED
ip address 10.251.21.10 255.255.255.240

interface Vlan23
ip vrf forwarding BLUE
ip address 172.27.12.254 255.255.255.0

router ospf 1 vrf RED
log-adjacency-changes
capability vrf-lite
network 10.251.21.0 0.0.0.15 area 2

router ospf 3 vrf BLUE
log-adjacency-changes
capability vrf-lite
network 172.27.12.0 0.0.0.255 area 2

Can the router take these VRF/OSPF instances and package them into BGP/MPLS to send across a WAN link using one subnet (peer-to-peer)? I want to cut down on all the subnets used for OSPF peering.

Amit Goyal · ‎12-09-2016

Hi Colin,

switch--OSPF in VRF (RED, BLUE)-->router(ASR)---MPLS----router---->switch

If above topology is correct,

1. Do you want to keep those two VRF instances separated on ASR? If yes then you will need two /30 subnets to form 2xeBGP peering in corresponding VRFs with MPLS provider.

But I hope this is not your purpose and you want to use only one subnet between Router and MPLS provider.

2. If you don't want to keep two VRF instances separate on ASR, you can simply build 2xOSPF neighbor ship in GRT (Global routing Table) on ASR and redistribute OSPF in eBGP formed with MPLS provider.

HTH

-Amit