what is the necessity of MPLS in below topology

[Muhammad Thanveer]

Hello Friends,

I have a topology attached

R1-------R2

R1 loopback 111 is in vrf A

R2 loopback 222 is in vrf A

i have isis and bgp vpnv4 configured and UP in R1 and R2. Now to reach loopback 111 from R2 and vice versa. do i need MPLS, If yes why? If no why?

[rtnet_4820]

Hello Thanveer,

you can use Cisco's implementation of VRF that is vrf-lite. This works without MPLS core. Additionally you don't need to configure MP-BGP VPNv4 for it.

[Muhammad Thanveer]

Hello Friend,

Thanks for replying. To be more specific you mean to say that if MP-BGP is configured do we need to run MPLS. If yes why?

If I am using vrf lite do I need to put the interfaces logical of Physical in the respective VRF?

BR

Mohammad Thanveer

[xthuijs · Accepted solution]

Hi Mohammad,

two separate PE's need to exchange their routing information for the vpn's configured.

the way to exchange that routing info is done via MPBGP. MP BGP assigns labels based on the prefix or vrf to signal to the remote PE to which vrf this new route belongs. Because it uses labels to associate prefixes and or vrf's you need to have MPLS enabled on the core interfaces as these guys need to understand how to interpret that labeled packet and how to switch it.

with vrf lite, what you'll do is you define a number of vlan subinterfaces on your core interfaces.

you assign the vrf to those vlan subs based on what is on your CE side. So you have a vlan per vrf.

if your network is small, it is doable, but this requires a lot of maintenance obviously. it is pretty much like old school PVC's in ATM, you need to relay on each hop and link the vrf subifs together and there is no redundancy then either easily.

MPLS enablement opens the door to dynamic provisioning, like sPVC's or soft PVC in ATM, you just define the endpoints and let the network in between figure it out.

cheers

xander