EVPN interoperability with VPLS

[emurray]

I am studying for the CCNP ISPCORE and i am configuring EVPN. I have configured EVPN so far with no problems but can't seem to make it work when one of the sites is using vpls. Many documents and presentations say there is interoperability, but I have not been able to make it work. 

PE running IOS XE

 l2vpn vfi context VPLS-EVPN_TEST
 vpn id 3091
 mtu 9180
 autodiscovery bgp signaling bgp 
  rd 10.0.0.1:3091
  route-target export 65000:3091
  route-target import 65000:3091
 member vfi VPLS-EVPN_TEST

Site with IOS XR running EVPN

 evpn
 ethernet-segment

 !
 evi 3091
  bgp
   rd 10.0.0.2:3091
   route-target import 65000:3091
   route-target export 65000:3091
  !
  description TEST VPLS EVPN
  advertise-mac
  !

I am able to ping on the sites that run EVPN but no with the one using the VPLS. Any help will be welcomed

[sidshas03]

Hi,

So, you’ve done a pretty good job setting up EVPN and VPLS separately, and you’re right – many documents do mention that EVPN and VPLS interoperate, especially in terms of MAC learning and BGP signaling. But practically, when one site is on IOS XE using VPLS and the other on IOS XR with EVPN, some compatibility issues often crop up. This is because EVPN uses Type 2 (MAC/IP Advertisement) and Type 3 (Inclusive Multicast Ethernet Tag) routes, whereas traditional VPLS using BGP doesn't understand these route types properly.

Your IOS XE VPLS config is using BGP for autodiscovery and signaling – that part is correct. But for proper interop with EVPN, especially with IOS XR on the other side, you'll need to enable EVPN signaling on the XE side too, because XR expects EVPN routes, not old-style VPLS ones.

Unfortunately, native interop between EVPN and VPLS works well when both ends support EVPN (with backward compatibility), but mixing classic VPLS with EVPN isn’t always seamless unless you’re using a gateway or doing some form of stitching between the two technologies, like:

• Interworking with bridge domains where you do local bridging between EVPN and VPLS instances on the same PE (if your platform allows).

• Or you may need to run both EVPN and VPLS on the same PE with separate bridge domains and stitch them together internally.

So, my suggestion is: if your hardware supports it, try enabling EVPN on the XE side also, or use a dedicated PE as an interop gateway that does EVPN to VPLS stitching. Also, check if the VPLS side is able to learn MACs from EVPN advertisements (use show bgp l2vpn evpn on XR and show l2vpn vfi on XE to debug MAC learning).