Proxmox: VMs and different public IPs

Question

I have a server which has two NICs and both are directly connected to internet. I have five different public IP addresses available for the VMs. The host machine (Proxmox) doesn't need to use any (it'll use a private IP and that's all) but will have internet connection.

I've gone through the Proxmox documentation and I'm not able to understand the big picture to set up the right network configuration for my needs. In short, what I have is:

• One server (Proxmox, host machine)
• On that server, 5 VMs are created
• 5 public IP addresses available (one for each VM), let's say: 80.123.21.1, 80.123.21.2, 80.123.21.3, 80.123.21.4, 80.123.21.5

What I have now for the host is the following:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual

auto eth1
iface eth1 inet manual

auto vmbr0
iface vmbr0 inet static
        address  192.168.1.101
        netmask  255.255.255.0
        bridge_ports eth0
        bridge_stp off
        bridge_fd 0

auto vmbr1
iface vmbr1 inet manual

It can be reached from the internal network, so that's OK. It has internet connection, which is also OK. vmbr1 is going to be used by the VMs. Each VM will have its own IP on his network interfaces configuration file.

For some reason, VMs will not have internet and they won't be able to have public IP address. If I use NAT, it will work correctly, but they will not use the public allocated IP addresses for them. Am I missing something?

Solution

You don't need to assign it a public IP address, but you do need to assign eth1 to a bridge port and give the other bridge options.

If you're new to proxmox, the webui supports managing ethernet interfaces and bridges for you. It also prevents you from naming your bridges poorly (proxmox enforces a vmbrNNNN, where the Ns are a number between 0 and 4095).

The interfaces file requires you provide an IP address for any defined interface, so to convince it otherwise you can add a local IP and just leave it, or as in this example, tear it down right away after the interface finishes coming up:

auto lo
iface lo inet loopback

iface eth0 inet manual
iface eth1 inet manual

auto vmbr0
iface vmbr0 inet static
        address  192.168.1.101
        netmask  255.255.255.0
        bridge_ports eth0
        bridge_stp off
        bridge_fd 0

auto vmbr1
iface vmbr1 inet static
       address  127.1.0.1
       netmask  255.255.255.255
       bridge_ports eth1
       bridge_stp off
       bridge_fd 0
       up ip addr del 127.1.0.1/32 dev vmbr1

Edit: Please edit your question if you are using any odd firewall rules that might block bridged traffic, and the value of sysctl net.ipv4.ip_forward.

You may want to tcpdump -n -i ethN (the external outgoing interface) to verify your packets are travelling off your host node.

Comments

[Nikita Kipriyanov]

Why adding and then removing address, when you could simply not add it at the first place? Use "iface vmbr1 inet manual" and you're done with this.

[Chaminda Bandara]

Then where is public IP address ? If I have multiple VM and multiple IP address how to do it please