Proxmox VE is using the Linux network stack. This provides a lot of flexibility on how to set up the network on the Proxmox VE nodes. The interfaces 5 manual page contains the complete format description. All Proxmox VE tools try hard to keep direct user modifications, but using the GUI is still preferable, because it protects you from errors.
A vmbr interface is needed to connect guests to the underlying physical network. They are a Linux bridge which can be thought of as a virtual switch to which the guests and physical interfaces are connected to. This section provides some examples on how the network can be set up to accomodate different use cases like redundancy with a bondvlans or routed and NAT setups.
This also allows to ensure your changes are correct before applying, as a wrong network configuration may render a node inaccessible. With the recommended ifupdown2 package default for new installations since Proxmox VE 7.
This will move changes from the staging interfaces. Another way to apply a new network configuration is to lag lacp wiki the node. In that case the systemd service pvenetcommit will activate the staging interfaces. This naming scheme is used for new Proxmox VE installations since version 5.
When upgrading to 5. This makes it easier to debug networks problems, because the device name implies the device type. Systemd uses the two character prefix en for Ethernet network devices. The next characters depends on the device driver and the fact which schema matches first.
For more information see Predictable Network Interface Names. Depending on your current network organization and your resources you can choose either a bridged, routed, or masquerading networking setup. The Bridged model makes the most sense in this case, and this is also the default mode on new Proxmox VE installations.
Each of your Guest system will have a virtual interface attached to the Proxmox VE bridge. This is similar in effect to having the Guest network card directly connected to a new switch on your LAN, the Proxmox VE host playing the role of the switch.
For this setup, you can use either a Bridged or Routed model, depending on what your provider allows. In that case the only way to get outgoing network accesses for your guest systems is to use Masquerading. For incoming network access to your guests, you will need to configure Port Forwarding.
That way it is possible to build complex and flexible virtual networks. Bridges are like physical network switches implemented in software. All virtual guests can share a single bridge, or you can create multiple bridges to separate network domains.