VxLan BGP EVPN with vPC broadcast storm problem

[MambaRod16]

Hello, 

We are implementing VXLAN BGP EVPN in our Datacenter. Our VXLAN Fabric consists of two Nexus 9364c Switches (Spines) and four Nexus C93108TC Switches (Leafs). The Leaf switches are forming two pairs of vPC VTEP Switches (Leaf1 with Leaf2) and (Leaf3 with Leaf4).

We have connectivity problems in the VxLan Fabric, when we connect a host on Leaf 3 or Leaf 4 we perceive packet losses. We monitored the traffic with Wireshark and observed there is an ARP broadcast storm which is saturating the fabric links. We tried turning off vpc on the Leaf-3 and Leaf-4 but the broadcast storm continues until we disconnect the host.

When we connect the host to Leaf-1 or Leaf-2 the communication is successfully.

- Which configuration could cause the creation of a broadcast storm in the Vxlan Fabric?

- Is there a limitation on using multiple vPC domain on a Vxlan fabric?

[MambaRod16]

Hello,

We have resolved the issue of the broadcast storm that was saturating our links within VXLAN.

Apparently the problem was that we were using PIM BiDir with Phanton-RP for the underlay network and it is possible that PIM BiDir had some conflict with the vPC configuration.

We proceeded to change the multicast mode from PIM BiDir (Phantom RP) to PIM-ASM with Anycast RP and the problem was solved immediately