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Mike
Asked: 2024-06-18 00:14:47 +0800 CST

NetworkManager not initializing VLAN interfaces on Debian 12

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Running Debian 12, my ethernet card gets an IP using DHCP, and I want to add a VLAN config to that same interface, VLAN 30, and assign it a static IP. Here's my /etc/network/interfaces:

auto lo
iface lo inet loopback

# The primary network interface
auto enp0s25
allow-hotplug enp0s25
iface enp0s25 inet dhcp

#VLAN
auto enp0s25.30
iface enp0s25.30 inet static
  address 192.168.30.2
  netmask 255.255.255.0
  gateway 192.168.30.1
 vlan-raw-device enp0s25

No amount of restarting NetworkManager or rebooting gets it to activate the enp0s25.30 interface. The NetworkManger log shows only this line relating to the .30 VLAN:

NetworkManager[2239]: <info>  [1718593439.7242] ifupdown: guessed connection type (enp0s25.30) = 802-3-ethernet

Note that my install uses NetworkManager and dhclient to configure interfaces. I don't have ifupdown installed. I don't have anything configured in dhclient.conf because I assumed NetworkManager would notice the 'inet static' and use that.

Also note that I have the following set in my NetworkManager.conf:

[ifupdown]
managed=true

I can get the interface up if I manually run:

ip link add link enp0s25 name enp0s25.30 type vlan id 30
ip addr add 192.168.30.2/24 dev enp0s25.30
ip link set dev enp0s25.30 up

but of course that doesn't persist after a reboot

Any help getting this working would be appreciated.

debian

2 Answers

  1. I got the same problem. Vlan does not activate. Also configures like yours in the interfaces.

    I solved this by using systemd-networkd service. interfaces seems to be deprecated in Debian 12 and only used for simple IP setting.

    Here is how i did it:

    1. Create the files you need:

    /etc/systemd/network/10-enp0s25.network

    [Match]
Name=enp0s25

[Network]
DHCP=yes
VLAN=enp0s25.30
    • This file defines your physical devices (network adapter) network in this case enp6s0. It should use DHCP and add an VLAN with the name enp6s0.3005. DHCP is only an example here. You can use static Stuff as well.

    Next as the Vlan is no physical device you need to add a virtual "netdev" device first to create the vlan.

    /etc/systemd/network/10-enp0s25.30.netdev

    [NetDev]
Name=enp0s25.30
Kind=vlan
MTUBytes=1400
[VLAN]
Id=30

    To finally create a network for the vlan device. This is done with a network file.

    /etc/systemd/network/10-enp0s25.30.network

    [Match]
Name=enp0s25.30
[Network]
Address=192.168.30.2/24
    1. Check the rights of these files

    They need to be 644. Otherwise systemd cant load them you get no network interface configured!

    1. Remove the old network stack and activate new one
    systemctl disable networking
mv /etc/network/interfaces /etc/network/interfaces.save
mv /etc/network/interfaces.d /etc/network/interfaces.d.save
systemctl enable systemd-networkd

    Now you can reboot and watch with a KVM if everything worked as it should.

    Vlan interfaces are now stable in my setup.

    • 0
  2. Best Answer

    Using systemd is a workable solution, but it doesn't solve the core problem.

    Also, NetworkManager can indeed use /etc/network/interfaces for it's configuration if the managed=true flag is set in /etc/NetworkManager/NetworkManager.conf.

    In my case it turned out NetworkManager already had a config for the ethernet interface in question configured in /etc/NetworkManager/system-connections. Apparently it must look in that location first, causing /etc/network/interfaces to be ignored.

    That said, I decided to use ifupdown2 for configuration instead of NetworkManager since this is a server, not a desktop, and will rarely see network changes.

    • 0