/etc/network/interfaces

[MagicCamera]

Will someone explain to me the dummy0 interface and how it is created? I have an OVH dedicated Proxmox server and the default installation has a dummy0 bridged on vmbr1. Where does it come from what is the purpose and how is it enabled?

I want to create an internal network bouncing off of the eth1 interface and maybe use a dummy1 to make it happen. So far I have searched high and low on the internet for any reference and so far nothing.

Any help in understanding the bridging features of proxmox is most welcomed.

The following is my default /etc/network/interfaces file:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# for Routing
auto vmbr1
iface vmbr1 inet manual <---PURPOSE OF THIS IN RELATION TO EVERYTHING ELSE
post-up /etc/pve/kvm-networking.sh <--THIS FILE DOESN'T EXIST... Can someone explain why?
bridge_ports dummy0 <---WHERE DOES THIS COME FROM AND HOW DOES IT RELATE TO eth0/vmbr0/vmbr1
bridge_stp off
bridge_fd 0


# vmbr0: Bridging. Make sure to use only MAC adresses that were assigned to you.
auto vmbr0
iface vmbr0 inet static
address my_public_ip
netmask 255.255.255.0
network my_public_ip.0
broadcast my_public_ip.255
gateway my_public_ip.254
bridge_ports eth0
bridge_stp off
bridge_fd 0

iface vmbr0 inet6 static
address ip6
netmask 64
post-up /sbin/ip -f inet6 route add ip6_info dev vmbr0
post-up /sbin/ip -f inet6 route add default via ip6_info
pre-down /sbin/ip -f inet6 route del default via ip6_info
pre-down /sbin/ip -f inet6 route del ip6_info dev vmbr0

 

[manu]

Hi
Proxmox do not install a vmbr1 bridge, this comes from the OVH template.
You can safely remove the vmbr1 bridge, and follow the instruction from https://pve.proxmox.com/wiki/Network_Model

 

[MagicCamera]

That is fine and dandy but it didn't work for me, in fact it zapped my whole system and I had to re-install. Thankfully though, I am at the testing and learning stage. Proxmox is actually a great piece of software, but the firewall input fields are confusing and I find it hard to translate to just entering them in manually, so why don't you create a text box input to a configuration file and please do explain in much much more detail how the firewall cascades down the line from Datacenter -> Node ->VMs. It's all very confusing.
I totally ignore your firewall and keep it off favouring instead to manually input rules and use iptables-persistent and pre-up the rules in the network interfaces config. And if you are going to tell a user just delete something, explain why, because I took your word as verbatum and it shot me in the foot.

I would ask that if you know a solution that would help someone share that knowledge with a good heart rather than feel that this person who needs the knowledge isn't paying for service, you might actually get a new paying customer out of it.

 

[wbumiller]

The dummy interface is a workaround to enable our old method of using vlans on bridges that aren't connected to physical interfaces (the code expects a physical interface to be present as we then setup separate bridges for vlans which get the vlan interface of this physical interface bound to them (ie eth0.1 => vmbr0v1)).
The default OVH setup does this to vmbr1, which has otherwise no purpose - at least none obvious to me - other than maybe giving you a head start for routed setups.
Now with only vmbr0 connected to the actual network, vmbr1 and dummy0 are not at all required for normal operation and removing them should not "zap" your entire system.
The dummy interface is only needed because debian's networking scripts require a bridge_ports option to be present for bridges. We also needed a port on bridges when using vlans before vlan-aware bridges appeared, btw. (`bridge_vlan_aware yes` in the /etc/network/interfaces file. (It's been a while since I removed it so I don't exactly remember where they created it. Either via simply autoloading the dummy module (/etc/modules-load.d/) as loading it automatically creates a dummy0, or some init script. You're gonna have to grep through /etc, sorry.)

Ah and as for the manual mode: that looks like a bug/typo from OVH.
And the post-up script... maybe a leftover line from some older image they created? Not sure.