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  • 1.  ESXi backup on Synology server.

    Posted May 31, 2023 01:25 PM


    I have a new ESXi 8.0.1 server that I just built on new HP hardware. I am trying to get the server backed up by my Synology backup server. I have two other ESXi servers that were running 7.0.3 and were backing up without an issue. They are still backing up without an issue after upgrading to 8.0.1. But the new 8.0.1 server will not back up. The Synology Active Backup for business will not connect to the server to catalog it for backup. I am able to ssh to the ESXi server from one of my computers but when I try to ssh into the ESXi from Synology it will not connect. I can not connect to the ESXi (HTTPS) server from a computer that is not on the same subnet as the ESXi server. Though I can SSH into the ESXi server from the same computer. All three ESXi server share adjacent IP addresses in the same subnet and the upgraded ones work fine but the new one will not. I am thinking there is some kind of a new security function in the ESXi 8.0 family that is stopping my access. 

    Does anyone have any suggestions on what I may need to do to get this working?

    Just for reference, the Synology server wants to have ports 443, 902, and 22 open to the ESXi server to allow the backup functions to run. I have verified that the ESXi server does have all three open on the firewall. The ESXi is protesting the opening of the SSH service in the management interface but is required for the backup to work.

  • 2.  RE: ESXi backup on Synology server.

    Posted May 31, 2023 08:32 PM

    Apparently, this was a bug in the Synology channel bonding. Resetting the MTU to the default of 1500 from the jumbo frames of 9000 resolved the issue.

  • 3.  RE: ESXi backup on Synology server.

    Posted Mar 19, 2024 03:06 PM

    Spotting the issue with your new ESXi 8.0.1 server's backup hiccup to Synology due to a MTU settings mismatch was sharp. It's a solid reminder that beyond the usual suspects like ports and firewalls, network settings like MTU size can silently derail connectivity. Always worth a check when new versions or hardware come into play and things don't line up as expected. Glad you cracked it and shared the fix.