Testing Multicast Operation of the underlying physical network in NSX VXLAN Deployments that do not have NSX controllers

Products

• VMware NSX

Issue/Introduction

Communication between VXLAN backed Guest VMs drop shortly after a vMotion Operation. The root cause may be the multicast based underlying physical network, which isn't correctly configured to properly support the multicast group. This procedure describes a test procedure to validate the physical network with a multicast group ping.

Environment

VMware NSX for vSphere 6.3.x
VMware NSX for vSphere 6.2.x

Resolution

How to test multicast operation:

1. Determine which vmk interface is the VTEP interface for VXLAN:

~ #  esxcli network ip interface ipv4 get -N vxlan

Name IPv4 Address   IPv4 Netmask  IPv4 Broadcast Address  Type  DHCP  DNS
---- ------------ ------------- -------------- ------------ --------------
vmk5 10.20.32.37    255.255.255.0    10.20.32.255            DHCP       false     Where vmk5 is the VTEP interface for VXLAN.

2. Identify two or more Guest VMs, on the same virtual wire, that have connectivity issues

locate this virtual wire sid, in this example it is 5549, which is the VXLAN identifier

3. Determine the Multicast Group IP for VXLAN 5549:

~ # net-vdl2 -l | grep -A5 5549
VXLAN network: 5549
Multicast IP: 225.x.x.6
Control plane: Disabled
MAC entry count: 3
ARP entry count: 0
Port count: 1   

- Multicast Group IP is 225.x.x.6

- VTEP interface is vmk5

4. Ping Multicast Group IP from VTEP interface:

Failed operation, only local host responds to group ping:

~ # vmkping ++netstack=vxlan -I vmk9 225.x.x.184

PING 225.x.x.184 (225.x.x.184): 56 data bytes

64 bytes from 10.20.32.150: icmp_seq=0 ttl=64 time=0.070 ms

64 bytes from 10.20.32.150: icmp_seq=1 ttl=64 time=0.060 ms

64 bytes from 10.20.32.150: icmp_seq=2 ttl=64 time=0.115 ms

 

When working, all multicast group member ESXi hosts respond to the ping, which will be reported as DUP, duplicate, responses:

~ # vmkping ++netstack=vxlan -I vmk9 225.x.x.184

PING 225.x.x.184 (225.x.x.184): 56 data bytes

64 bytes from 10.20.32.150: icmp_seq=0 ttl=64 time=0.068 ms

64 bytes from 10.20.32.24: icmp_seq=0 ttl=64 time=0.291 ms (DUP!)

64 bytes from 10.20.32.37: icmp_seq=0 ttl=64 time=0.381 ms (DUP!)

64 bytes from 10.20.32.150: icmp_seq=1 ttl=64 time=0.466 ms

64 bytes from 10.20.32.37: icmp_seq=1 ttl=64 time=0.520 ms (DUP!)

64 bytes from 10.20.32.24: icmp_seq=1 ttl=64 time=0.531 ms (DUP!)

64 bytes from 10.20.32.150: icmp_seq=2 ttl=64 time=0.067 ms

64 bytes from 10.20.32.37: icmp_seq=2 ttl=64 time=0.260 ms (DUP!)

64 bytes from 10.20.32.24: icmp_seq=2 ttl=64 time=0.357 ms (DUP!)