Network issues Windows VM migrated from ESXi

[etfz]

Hi,

I have imported an ESXI VM. I use VirtIO for the network adapter. On first boot after migrating and installing VirtIO drivers, it is correctly assigned a DHCP address, but traffic does not work. I can't reach any external devices, including the gateway. From here on things get very inconsistent, but:

- Reboot usually does not help.
- Disabling and enabling the network adapter usually fixes it, but sometimes only for a few seconds.
- Using vmxnet3 does not fix it.
- Resetting MAC address does not fix it.
- Once working, temporarily cutting its network connection externally (either on the Proxmox level or at the upstreams router) again breaks it.

I have another VM imported from the same source machine where it works better, but the configuration should be identical. Comparing the configuration files, only the MAC address and other IDs differ.

PVE 9.0.5.

 

[Onslow]

Hi, etfz. The symptoms you described may indicate that it's the IP address conflict.
As the VM gets the address from DHCP, maybe there is some device in the network, which has a static IP address (not from DHCP) and this address is in the DHCP range.

A basic check would be switching off the VM and pinging its IP address. Successful ICMP replies would mean that this address is used also elsewhere.
Note that this check may be not sufficient because that other device might not answer to ping - for various reasons.

 

[etfz]

Hi,

Thanks for your response. There are no statically addressed devices on the network in question, except the gateway. I get no response pinging the address, whether the VM is running or no. I did notice that pings are blocked by default, which is surprising, (Windows Server 2025) but I enabled it, and it works on the other VM.

It seems like installing the guest agent might have resolved the issue, but I don't know why the other VM did not require it.