Tag VLAN ID for Proxmox Management Interface
For a project I’m working on, I needed to set up a VLAN-tagged Proxmox management interface using Linux Bridges. I had previously used a similar setup with Open vSwitch and assumed it would be the same with Linux Bridges. However, I encountered issues when trying to assign an IP from the management VLAN to the Proxmox host and create a management VLAN for VMs using SDN.
IP Assigned to Linux Bridge
In a default Proxmox installation, the IP address provided during the hypervisor setup is assigned to a “Linux Bridge” interface linked to the physical port. Assuming there are no VLANs involved and we are working with a flat network for the management interface, the configuration looks straightforward.
/etc/network/interfaces
auto lo
iface lo inet loopback
iface enp129s0f0np0 inet manual
iface enp129s0f1np1 inet manual
auto eno1
iface eno1 inet manual
iface eno2 inet manual
iface eno3 inet manual
iface eno4 inet manual
auto vmbr0
iface vmbr0 inet manual
address 10.12.1.11/24
gateway 10.12.1.1
bridge-ports eno1
bridge-stp off
bridge-fd 0
source /etc/network/interfaces.d/*
IP Assigned to VLAN Interface
Now, let’s consider that the management network belongs to a VLAN, and we need to assign an IP from that VLAN to Proxmox to access the web UI. So in the previous configuration, mark the bridge as VLAN aware and then add a "Linux VLAN" interface.
I named this interface "pve" to assign an IP from VLAN 99 to our Proxmox host.
/etc/network/interfaces
auto lo
iface lo inet loopback
iface enp129s0f0np0 inet manual
iface enp129s0f1np1 inet manual
auto eno1
iface eno1 inet manual
iface eno2 inet manual
iface eno3 inet manual
iface eno4 inet manual
auto vmbr0
iface vmbr0 inet manual
bridge-ports eno1
bridge-stp off
bridge-fd 0
bridge-vlan-aware yes
bridge-vids 2-4094
auto pve
iface pve inet static
address 10.12.99.12/24
gateway 10.12.99.1
vlan-id 99
vlan-raw-device vmbr0
#Proxmox Management
source /etc/network/interfaces.d/*
IP Assigned to VLAN Interface + SDN
The problem arose when I tried to assign an IP from the management VLAN to the Proxmox host while also creating a management VLAN for VMs using SDN. With the above setup, I created a SDN VNet called "mgmt".
The goal was to be able to assign IP from management VLANs to Virtual Machines. But instead, I lost access to the Proxmox node. I had to drop into Linux terminal and try to manually restart networking service which created all kinds of weird behavior ranging from the host management IP being unavailable, to the SDN interface not providing management network to VMs.
After a lot of headscratching and going through Proxmox documents and forums, I came across this bug report.
Essentially, adding a VNet from the GUI creates following configuration in /etc/network/interfaces.d/sdn
auto mgmt
iface mgmt
bridge_ports vmbr0.99
bridge_stp off
bridge_fd 0
alias Management Network
This conflicts with our previously created Linux VLAN. The solution for now is to use the same name for SDN VNet and Linux VLAN.
Potential Workaround
This cannot be done via the GUI and needs to be done by manually editing /etc/network/interfaces. Change pve (Linux VLAN interface name) to mgmt (SDN VNet interface name) and remove details of the parent interface as this would be referenced from the SDN configuration. Thus my final configuration looks like:
/etc/network/interfaces
auto lo
iface lo inet loopback
iface enp129s0f0np0 inet manual
iface enp129s0f1np1 inet manual
auto eno1
iface eno1 inet manual
iface eno2 inet manual
iface eno3 inet manual
iface eno4 inet manual
auto vmbr0
iface vmbr0 inet manual
bridge-ports eno1
bridge-stp off
bridge-fd 0
bridge-vlan-aware yes
bridge-vids 2-4094
auto mgmt
iface mgmt inet static
address 10.12.99.12/24
gateway 10.12.99.1
#Proxmox Management
source /etc/network/interfaces.d/*
/etc/network/interfaces.d/sdn
auto mgmt
iface mgmt
bridge_ports vmbr0.99
bridge_stp off
bridge_fd 0
alias Management Network
auto nihar
iface nihar
bridge_ports vmbr0.30
bridge_stp off
bridge_fd 0
alias Nihar Lab
auto pkt0
iface pkt0
bridge_ports vmbr0.50
bridge_stp off
bridge_fd 0
alias PKT0
auto pkt1
iface pkt1
bridge_ports vmbr0.51
bridge_stp off
bridge_fd 0
alias PKT1
auto sweha
iface sweha
bridge_ports vmbr0.52
bridge_stp off
bridge_fd 0
alias SWE HA
The only side effect I noticed so far with this workaround is that the VLAN interface in Proxmox GUI shows up as Unknown.
