Use one main MAC address of the server for all IP machines


May 6, 2017
I have a server from hetzner, and install proxmox on it.

My configuration is simple, and it's my "/etc/network/interfaces" file:

auto lo
iface lo inet loopback

iface enp6s0 inet manual

auto vmbr0
iface vmbr0 inet static
        address XX.YY.ZZ.TT
        gateway XX.YY.ZZ.DD
        bridge_ports enp6s0
        bridge_stp off
        bridge_fd 0
        bridge_maxwait 0

And also I have one additional subnet /28, and can use these IP range in VMs and works well for few months.
And you know that each machine has a different and independent MAC address.

Today my server was suspended!

This is email from hetzner:

We have noticed that you have been using other MAC addresses in addition to the allowed at your Robot account.

Allowed MAC addresses:
not allowed MAC addresses:

We see wrong MACs on your switchport at this very moment:

YY:YY:YY:YY:YY:YY D - ge-0/0/39.0<<<---not allowed
XX:XX:XX:XX:XX:XX D - ge-0/0/39.0

The Problem is that you use this MAC towards our Switch.

For your subnet IPs you need to use the Main MAC of the Server to communicate towards the internet in order to solve the problem.

You should apply a routed setup for your additional subnet.

Please check this with tcpdump on your server.

I assigned the main MAC address to the virtual machine, but the virtual machine gave timeout, and it seems that the machine MAC should not be the same with the main server MAC address.

This is an emergency problem.
How can I solve the problem please?


The Proxmox community has been around for many years and offers help and support for Proxmox VE, Proxmox Backup Server, and Proxmox Mail Gateway.
We think our community is one of the best thanks to people like you!

Get your subscription!

The Proxmox team works very hard to make sure you are running the best software and getting stable updates and security enhancements, as well as quick enterprise support. Tens of thousands of happy customers have a Proxmox subscription. Get yours easily in our online shop.

Buy now!