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systemd-networkd and debian 13

created: 2026-08-03

I moved away from Debian’s network interface configuration and to systemd-networkd.

Using standard systemd-networkd config in Debian 13, on a router I’ve been able to:

setup bridging
support multiple VLANs on bridge interface
support IPv6 prefix delegation with multiple prefixes

Network diagram below details the final setup. The router running debian 13 has eth0 which is connected to LAN and eth1 connected to WAN. The ISP provides a dynamic /40 prefix. LAN has 3 VLANs with clients in each VLAN. The switch trunk port that eth0 is connected to is tagging all 3 VLANs.

                        ┌───────────┐
                        │  router   │
                        └─────┬─────┘
                              │
      ┌───────────────────────┴───────────────────────┐
      │                                               │
 [ WAN Interface ]                              [ LAN Interface ]
      eth1                                           eth0
      │                                               │
      │                                               ▼
      │                                         ┌───────────┐
      │                                         │    br0    │
      │                                         │ (Bridge)  │
      │                                         └─────┬─────┘
      │                                               │
      │             ┌─────────────────────────────────┴─────────────────────────────────┐
      │             │                                 │                                 │
      ▼             ▼                                 ▼                                 ▼
┌───────────┐ ┌───────────────┐                    ┌───────────────┐                 ┌────────────────┐
│    ISP    │ │   vlan1       │                    │   vlan10      │                 │   vlan20       │
│  Gateway  │ │ 192.168.1.1   │                    │ 192.168.10.1  │                 │ 192.168.20.1   │
│           │ │ 2001:db8:1::1 │                    │ 2001:db8:10::1│                 │ 2001:db8:20::1 │
└───────────┘ └───────────────┘                    └───────────────┘                 └────────────────┘
                     │                                 │                                 │
                     ▼                                 ▼                                 ▼
                [ VLAN 1 ]                        [ VLAN 10 ]                        [ VLAN 20 ]
                 (Clients)                         (Clients)                         (Clients)

Setup the virtual network device for br0 as a bridge.

/etc/systemd/network/br0.netdev

[NetDev]
Name=br0
Kind=bridge

Each VLAN will also need it’s own virtual network device.

/etc/systemd/network/20-vlan1.netdev

[NetDev]
Name=vlan1
Kind=vlan

[VLAN]
Id=1

/etc/systemd/network/20-vlan10.netdev

[NetDev]
Name=vlan10
Kind=vlan

[VLAN]
Id=10

/etc/systemd/network/20-vlan20.netdev

[NetDev]
Name=vlan20
Kind=vlan

[VLAN]
Id=20

eth0 needs to be setup as an enslaved interface to br0

/etc/systemd/network/10-eth0.network

[Match]
Name=eth0

[Network]
Bridge=br0

br0 network configuration needs to list the VLANs that it bridges. /etc/systemd/network/20-br0.network:

[Match]
Name=br0

[Network]
VLAN=vlan1
VLAN=vlan10
VLAN=vlan20
LinkLocalAddressing=no

eth1 network configuration will obtain IPv4 and IPv6 addresses via DHCP. /etc/systemd/network/eth1.network:

[Match]
Name=eth1

[Network]
DHCP=yes
IPv6AcceptRA=yes
DHCPPrefixDelegation=yes

[DHCPv6]
PrefixDelegationHint=::/64
UseDelegatedPrefix=yes

Each VLAN interface will need its own network configuration file. /etc/systemd/network/40-vlan1.network

[Match]
Name=vlan1

[Network]
Address=192.168.1.1/24
IPv6SendRA=yes
IPv6AcceptRA=no
DHCPPrefixDelegation=yes

[DHCPPrefixDelegation]
SubnetId=0x1
Assign=yes
Token=::1

/etc/systemd/network/40-vlan10.network

[Match]
Name=vlan10

[Network]
Address=192.168.10.1/24
IPv6SendRA=yes
IPv6AcceptRA=no
DHCPPrefixDelegation=yes

[DHCPPrefixDelegation]
SubnetId=0x10
Assign=yes
Token=::1

/etc/systemd/network/40-vlan20.network

[Match]
Name=vlan20

[Network]
Address=192.168.20.1/24
IPv6SendRA=yes
IPv6AcceptRA=no
DHCPPrefixDelegation=yes

[DHCPPrefixDelegation]
SubnetId=0x20
Assign=yes
Token=::1

Once systemd-networkd has been restarted, networkctl should present the following:

# networkctl list
IDX LINK   TYPE      OPERATIONAL SETUP
  1 lo     loopback  carrier     unmanaged
  2 eth0   ether     enslaved    configured
  3 br0    bridge    carrier     configured
  4 vlan20 vlan      routable    configured
  5 vlan10 vlan      routable    configured
  6 vlan1  vlan      routable    configured
  7 eth1   ether     routable    configured