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Configuring vSAN Unicast networking from the command line (2150303)

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This article provides information about configuring vSAN Unicast networking from the command line.

Note: vSAN Unicast mode is a new feature of vSAN 6.6 that was introduced to simplify the network requirements of a vSAN cluster by replacing the legacy multicast framework previously used to achieve quorum. 


After you upgrade or install vSAN 6.6 and complete the on-disk upgrade, your cluster should switch over automatically to unicast. If additional vSAN 6.6 nodes are added, they should inherit unicast configuration from vCenter automatically. In some cases the list of vSAN nodes maintained by vCenter and the number of actual nodes may differ due to nodes being added or removed while vCenter is unavailable. If this occurs, you may need to consider updating the unicast neighbour list manually. The following commands may help with manual configuration.

Adding unicast neighbors manually: 

esxcli vsan cluster unicastagent add -t node -u <uuid> -U <unicastSupport> -a <ip> -p <port> -i <interface>
esxcli vsan cluster unicastagent add -t node -u 57ea62b0-9df6-6532-110c-9457a55a37d0 -U true -a XX.XXX.XXX.XX-p 12321 -i vmk3

Note: If you need to configure unicast mode manually to bypass vCenter, you should set /vSAN/IgnoreClusterMemberListupdates to a value of 1 on every node in the cluster to prevent vCenter from automatically overwriting your configuration. This value should be flipped back to 0 after the vCenter Server is back with the correct hosts in the inventory list.
[root@esxp8mg014:/tmp] esxcfg-advcfg -s 1 /VSAN/IgnoreClusterMemberListupdates
Value of IgnoreClusterMemberListUpdates is 1
You will also need to run the preceding command several times on each host in the cluster in order to build the unicast neighbor list manually as each node needs to be aware of all of the other nodes in the cluster. 

The help menu explains what each of these switches does, for reference: 

  -a|--addr=<str>       IP address of the unicast agent. (required)
                        Name of the bound outgoing network interface.
  -p|--port=<long>      Port the unicast agent is listening on.
  -U|--supports-unicast Whether the software version supports unicast (required for -t node)
  -t|--type=<str>       Type of the unicast agent (One of  [witness, node], default is witness).
  -u|--uuid=<str>       UUID of the unicast agent (required for -t node)

Manually removing a neighbor node
esxcli vsan cluster unicastagent remove -t node -u <uuid> -i, or -p for port number or -a for address

Listing all neighboring nodes
esxcli vsan cluster unicastagent list 

example output: 

NodeUuid                              IsWitness  Supports Unicast  IP Address       Port  Iface Name
------------------------------------  ---------  ----------------  --------------  -----  ----------
58822d03-4cf9-e882-c954-246e9609a848          0              true  12321
58821f28-6b12-2997-54ac-246e9609f270          0              true  12321
58824739-4694-5be8-0d70-246e96099fd8          0              true  12321
58ad6d9e-28ec-69be-30eb-246e9609f308          0              true  12321

Additional Information

If you find that you have completed your upgrade to vSAN 6.6 including the on-disk upgrade process and your hosts are still utilizing multicast for cluster communications, confirm that you do not have an orphaned/dead host information stuck in cmmds as this can prevent the conversion from occurring naturally. 

VMware does not support reverting back to multicast mode after the vSAN 6.6 installation or upgrade has completed and unicast mode has been successfully configured.

See Also

Request a Product Feature

To request a new product feature or to provide feedback on a VMware product, please visit the Request a Product Feature page.


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