VSAN-Troubleshooting-Reference-Manual

Diagnostics and Troubleshooting Reference Manual – Virtual SAN
Troubleshooting a multicast configuration issue
As mentioned, a common issue is that the Virtual SAN Cluster is configured across
multiple physical switches, and while multicast has been enabled on one switch, it
has not been enabled across switches. In this case, the cluster forms with two ESXi
hosts in one partition, and another ESXi host (connected to the other switch) is
unable to join this cluster. Instead it forms its own Virtual SAN cluster in another
partition. Remember that the vsan.lldpnetmap command seen earlier can assist in
determining network configuration, and which hosts are attached to which switch.
Symptoms of a multicast misconfiguration issue
Other than the fact that the Virtual SAN Cluster status displays a network
misconfiguration issue, there are some other telltale signs when trying to form a
Virtual SAN Cluster that multicast may be the issue. Assume at this point that the
checklist for subnet, VLAN, MTU has been followed and each host in the cluster can
vmkping every other host in the cluster.
If there is get a network misconfiguration detected when the cluster is formed, the
next symptom you will observe is that each ESXi host forms its own Virtual SAN
cluster, with itself as the master. It will also have a unique network partition id. This
symptom suggests that there is no multicast between any of the hosts.
However if there is a situation where a subset of the ESXi hosts form a cluster, and
another subset form another cluster, and each have unique partitions with their
own master, backup and perhaps even agent nodes, this may very well be a situation
where multicast is enabled in-switch, but not across switches. In situations like this,
Virtual SAN shows hosts on the first physical switch forming their own cluster
partition, and hosts on the second physical switch forming their own cluster
partition too, each with its own “master”. If you can verify which switches the hosts
in the cluster connect to, and hosts in a cluster are connected to the same switch,
then this may well be the issue.
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