Not able to add remote ESXI host to vCenter

[KarmaT]

I am not able to add a remote ESXI host to vCenter. Error message:

"Cannot contact the specified host (x.x.x.x). The host may not be available on the network, a network configuration problem may exist, or the management services

on this host may not be responding."

I have added another remote ESXI host to the vCenter earlier without any issue. All the network configurations are same for both the ESXI hosts. I restarted the management agents on the ESXI host as well. However, the issue still persists. Effective resolution needed.

[Sreejesh_D]

Hi Karma,

are you able to ping the host with IP and name from the vCenter server (vcsa or winidows)? if not, we've to look at the network connectivity between the vCenter and the host.

[vijayrana968]

Did you made any recent changes to host ? Try some primary troubleshooting steps :

1. Ping Host name from vCenter with IP address and Host Name both. It should be reachable via both.

2. Check ESXI host is connecting directly through vSphere Client.

3. Make sure host network configuration is correct and unique.

       System Customization > Configure management network : Make sure IP address and Host name is unique. Also add DNS suffix there

       System Customization >  Test Management Network :  After network configuration, run this test to ensure your configuration is valid and correct.

      

[vembutech1]

Check from vCenter server, the host is reachable. Ping host with its IP and name. Is the host on another network, and route exist between the vCenter and host network ?. Most likely network routing issue. Find any firewall in between which dening to connect.

[dekoshal]

Follow Below Mentioned VMware KB article in sequence.

Testing network connectivity with the ping command (1003486) | VMware KB

Testing port connectivity with Telnet (1003487) | VMware KB

Restarting the Management agents in ESXi (1003490) | VMware KB

Reference KB article

Troubleshooting an ESXi/ESX host in non responding state (1003409) | VMware KB

If you found this or any other answer helpful, please consider the use of the Helpful to award points.

Best Regards,

Deepak Koshal

CNE|CLA|CWMA|VCP4|VCP5|CCAH

[Techstarts]

Thanks, your tips and links helped me a lot

[lajato]

For anyone who is looking for a solution to this problem, tried everything they could find online but without success:

Your vCenter and the host you're trying to add are probably not on the same LAN but connected with a VPN.  Lower the MTU of the tunnel to less then 1320. This will solve the issue.

[Dawnwater]

So much thanks..it solved my issue

[Dan_Farkas]

I literally made an account just to say thank you thinks worked!!

For me this showed up as a problem right after a building move and we had copper site-to-site in the new building, where the hosts were not connecting, while we wait for fiber. I lowered the MTU and bang, zoom. Connected no problem! I'll change it back once we're on fiber but this got me going. Thanks! 

[VMware_Download]

A few years later, but for anyone coming to this from vSphere 8 -- lajato's resolution was spot-on.

Our setup has a vCenter in the U.S. and a remote cluster in Europe -- connection between the two is over an SDWAN/VPN connection.  ESXi sleds would show when you tried to add them to the vCenter, request user/pw, and present thumbprints for verification -- but once verified/logged in, the connection was lost and after hitting "OK" to add them to the vCenter datacenter/cluster, they remained stuck at 0% until they timed out.

Resolution was going into the server and client config files, and lowering the fragment down to the necessary level -- in our case, 1340.  With that done and the VPN services restarted, the ESXi hosts were successfully added to the vCenter cluster without issue.

[PeterWoo339]

my case is that I cloned esxi host in vmware workstation, and the clone has the same mac, so the vCenter on one of the esxi host cannot add the other esxi host...