Then verify that there are no actual communication issues between the data nodes and the witness appliance before proceeding. (See
Testing VMkernel network connectivity with the vmkping command (1003728) for more details on using vmkping)
To verify connectivity perform vmkping tests between the vsan vmks.
To test 1500 MTU, run the command: vmkping -I vmkX x.x.x.x -d -s 1472 To test 9000 MTU, run the command: vmkping -I vmkX x.x.x.x -d -s 8972
In addition, check the connectivity between the witness appliance and the data nodes via port 12321.
On the witness: tcpdump-uw -i vmkX (vmkx is the vmk port that is used for witness traffic)
If there is connectivity you will see incoming requests and responses over port 12321
Example:
On the data node: tcpdump-uw -i vmkX | grep <witness IP> (vmkX is the vmk for witness traffic)
If working correctly, you will see it reaching out over port 12321 and also the response.
Example:
![](https://api-broadcomcms-software.wolkenservicedesk.com/attachment/get_attachment_content?uniqueFileId=1512261140527)
If there is no connectivity over port 12321, get this resolved first. If there is connectivity proceed.
Once this is verified follow these steps:
1. Put the witness appliance in maintenance mode with Ensure Accessibility
2. Disable the stretched cluster in the GUI. Configure > VSAN > Fault Domains and Stretched Clusters
3. SSH Into the witness appliance and manually dismantle the disk group. (See
How to manually remove and recreate a vSAN disk group using esxcli (2150567) for details on this process)