Migrating VMs from 8.4 to 9.0

[ljhardy]

I have an 8.4 cluster and I've added new nodes running 9.0. I'm trying to migrate a VM from an 8.4 node to a 9.0 node and am getting this error message when the VM tries to start on the 9.0 node:

2025-09-16 19:30:21 starting VM 111 on remote node 'proxmox11'
2025-09-16 19:30:23 [proxmox11] Unknown option: nets-host-mtu
2025-09-16 19:30:23 [proxmox11] 400 unable to parse option
2025-09-16 19:30:23 [proxmox11] qm start <vmid> [OPTIONS]
2025-09-16 19:30:23 ERROR: online migrate failure - target node proxmox11 is too old for preserving VirtIO-net MTU, please upgrade

Am I totally off here on how to migrate these VMs from 8.x to 9.x in this manner?

**SOLVED, specified MTU = 1500 on the existing VM on the Proxmox 8.4 node.

 

[fiona]

Hi,
it should also work if you upgrade the 9.x node to the latest version.