Posted on January 11, 2021 8:19 am
 |  Asked by OPTIVER OPTIVER
 |  75 views
0
0
Print Friendly, PDF & Email

We have a spine and leaf topology, where we have several VRFs. We’re currently using VRF-lite, with EBGP peerings per-VRF between spines and leaves.

 

We are using Multicast in all VRFs. The Rendezvous Points are Loopback addresses in the Spines, and they use anycast-rp addresses. PIM neighborhoods are being formed, everything works as expected.


router multicast
vrf VRF_A
ipv4
routing
!
vrf VRF_B
ipv4
routing
!
vrf VRF_C
ipv4
routing
!
router pim sparse-mode
vrf VRF_A
ipv4
rp address 172.16.100.101 239.240.240.0/24
anycast-rp 172.16.100.101 10.10.10.1
anycast-rp 172.16.100.101 10.10.10.2
!
vrf VRF_B
ipv4
rp address 172.16.100.102 239.240.240.0/24
anycast-rp 172.16.100.102 10.10.20.1
anycast-rp 172.16.100.102 10.10.20.2
!
vrf VRF_C
ipv4
rp address 172.16.100.103 239.240.240.0/24
anycast-rp 172.16.100.103 10.10.30.1
anycast-rp 172.16.100.103 10.10.30.2

 

Now we’ve decided to test a EVPN configuration. We’ve configured EVPN with 1 interface Vxlan per device, and 1 VNI per VRF. We don’t have stretched VLANs (so there are no VNIs for VLANs), since we just need to advertise EVPN ipv4 prefixes.

We are essentially using VxLAN + EVPN to build a L3VPN. This shows all the advertised prefixes.

show bgp evpn route-type ip-prefix ipv4

All VRF routes are being propagated across all devices, and there is IP reachability between all of them, to all destinations, including the Spine Loopback IPs that will serve as RPs. However, now the PIM neighborhoods don’t come up now.

show ip pim vrf VRF_A neighbor

Can you tell us what needs to be done so multicast can work on the overlay VRFs?
We are running EOS 4.22.2M on 7050 (leaves) and 7304 (spines). Thanks.

0
Posted by Aniket Bhowmick
Answered on January 11, 2021 8:28 am

Hi Optiver

Thank you for posting your query !

Can you please answer our below questions so we get better context :

  • I believe you are trying to form PIM neighbourship via Vxlan overlay SVI. This means your PIM packets would get encapsulated in Vxlan using the VRF VNI that you have configured on all VTEPs. Is this correct ?
  • Or are you trying to form the PIM neighbourship on underlay network (between Leaf and Spine) which won't get encapsulates in Vxlan?
  • If you are using overlay Vlan/SVI to form the PIM neighbour- are you using "ip address virtual" command on the SVI  or some other command (like "ip virtual-router address") ?
  • If you are forming the PIM neighbourship between Leaf and Spine (underlay), are you using subinterfaces so that you can use multiple VRFs on the same link ? (ignore if you are using overlay PIM)
  • Is it possible for you to share the output of "show tech-support | no" with us and also the output of "sh ip pim vrf  <vrf_name> neighbor detail" ?

Regards,

Aniket

0
Posted by Ashish A Majumdar
Answered on January 12, 2021 12:40 am

I am assuming that with EVPN you have removed the VRF-lite configuration from the leaf/spine links and are now using the EVPN with symmetric IRB with overlay (L3 VNI) to provide segregation in the overlay.

If the above is true you are looking at supporting multicast with EVPN you may want to have a look at EVPN multicast, support for which was added in EOS 4.25.1F. This image supports multicast via type 6,7.8 and 10 and an updated type 3 route-types.

Kindly get in touch with your account team to get more details.

 

 

 

 

 

0
Posted by OPTIVER OPTIVER
Answered on January 12, 2021 5:15 pm

Thanks for your detailed reply.

  • Q: I believe you are trying to form PIM neighbourship via Vxlan overlay SVI. (...)
  • A: Yes, this was what I did to make the PIM neighborhoods work. At the time I opened this ticket I had incomplete configs, but I've since created a core-VLAN, enabled PIM in the switches SVIs, and now PIM neighbors are up.

As far as I understand, I have 3 methods of making multicast work:

  1. Using sub-interfaces in the underlay (a solution like VRF-lite) -> which I don't want (avoiding fabric sub-interfaces is one of the reasons I'm trying EVPN)
  2. Using an overlay core-VLAN per VRF for PIM neighborhoods using SVIs -> which is what I did
  3. Using EVPN route types 6-8 -> which I haven't tried since it's not yet supported in EOS 4.23.5M

Between methods 2 and 3, which one would be recommended by Arista? Is there any advantage or drawbacks of one method over the other? I'd be more willing to chose whatever solution offers better performance and stability.

 

Appreciate any advice, thanks.

Post your Answer

You must be logged in to post an answer.