vSphere HA agent on this host could not reach isolation address <IP Address>'" in the vCenter server
Article ID: 412554
Updated On:
Products
Issue/Introduction
In the vCenter user interface, in the Hosts and Clusters view, with the ESXi host selected, you see the message "vSphere HA agent on this host could not reach isolation address <IP Address>
Environment
VMware vSphere ESXi 7.0
VMware vSphere ESXi 8.0
Cause
The ESXi host is unable to establish network connectivity to the defined isolation address indicated in the error message.
By default in a non-vSAN environment - Typically the management gateway is used by default. Host - configure - network - TCP/IP configuration.
In other cases in non-vSAN and vSAN environments - specific isolation addresses are configured with custom multiple IP addresses (see KB)
https://knowledge.broadcom.com/external/article/341627/setting-multiple-isolation-response-addr.html
In vSAN environments - isolation addresses work in a similar way (see KB) https://knowledge.broadcom.com/external/article?articleId=313763
Resolution
Verify network connectivity is possible from the host for whatever the isolation address is not reachable for in the error message. It may be necessary to check connectivity to the isolation address from a specific VMkernel Adapter. This may vary from in individual customer environments
From host CLI confirm network Connectivity to the host from VMK adapter
vmkping -I vmk<#> <Isolation_Address>
Additional Information
For more information on using CLI command: vmkping, please reference the following article: Troubleshooting network and TCP/UDP port connectivity issues on Hosts
After confirming network connectivity is possible to the Isolation address from the hosts vmk interface and the error message is still presenting on the ESXi host, please proceed with verifying: vSphere HA agent on this host could not reach isolation address '#.#.#.#', reported on ESXi host
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