Hi,

I have Debian Trixie with KDE installed on my local HP Z440 workstation.

In the default configuration network is managed by NetworkManager. I
have a router in my local network, and the workstation is a DHCP client.

# ip -brief -family inet address show
lo UNKNOWN 127.0.0.1/8
enp3s0 UP 192.168.2.3/24
# nmcli con show
NAME UUID TYPE DEVICE Wired connection 1 bfe0ecbc-1a65-4487-b7d8-5aaa563286ff ethernet enp3s0
lo 3552564c-088e-4907-ad2d-3b285a8439cc loopback lo

I'd like to create a br0 bridge with enp3s0 as a bridge slave, so I can
have virtual machines on this machine connect to the local network.

What's the Debian way of doing this? Create a bridge with NetworkManager
using nmtui? Edit /etc/network/interfaces or some configuration file
stub around there?

I'm a long-time Linux user (25 years of experience) but I'm just back
from a very (!) long break from Debian.

Cheers,

Niki

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--- PyGate Linux v1.5.2
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Nicolas Kovacs wrote:

I have Debian Trixie with KDE installed on my local HP Z440 workstation.

In the default configuration network is managed by NetworkManager. I have a router in my local network, and the workstation is a DHCP client.

# ip -brief -family inet address show
lo UNKNOWN 127.0.0.1/8
enp3s0 UP 192.168.2.3/24
# nmcli con show
NAME UUID TYPE DEVICE Wired connection 1 bfe0ecbc-1a65-4487-b7d8-5aaa563286ff ethernet enp3s0
lo 3552564c-088e-4907-ad2d-3b285a8439cc loopback lo

I'd like to create a br0 bridge with enp3s0 as a bridge slave, so I can have virtual machines on this machine connect to the local network.

What's the Debian way of doing this? Create a bridge with NetworkManager using nmtui? Edit /etc/network/interfaces or some configuration file stub around there?

If you control the router/DNS/DHCP, then the best move is to
drop NetworkManager and use /etc/network/interfaces:

auto enp3s0
auto br0
iface br0 inet static
bridge_ports enp3s0
address 192.168.2.3
netmask 255.255.255.0
gateway 192.168.2.1

If you don't control DHCP and have to use it, stick with
NetworkManager.


-dsr-

--- PyGate Linux v1.5.2
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Le 13/01/2026 … 17:15, Dan Ritter a ‚critÿ:

If you control the router/DNS/DHCP, then the best move is to
drop NetworkManager and use /etc/network/interfaces:

auto enp3s0
auto br0
iface br0 inet static
bridge_ports enp3s0
address 192.168.2.3
netmask 255.255.255.0
gateway 192.168.2.1

I tried what you suggested, and I have a weird result. It works, but I
get an error message.

# ip -brief -family inet address show
lo UNKNOWN 127.0.0.1/8
br0 UP 192.168.2.3/24

On startup there was a little hiccup with a little red error instead of
a green OK. So I checked, and here it is:

# journalctl -p err
...
Jan 14 08:37:35 sandbox systemd[1]: Failed to start networking.service -
Raise network interfaces.

Any idea what's causing this error message ?

Cheers,

Niki

--
Microlinux - Solutions informatiques durables
7, place de l'‚glise - 30730 Montpezat
Site : https://www.microlinux.fr
Blog : https://www.microlinux.fr/blog
Mail : info@microlinux.fr
T‚l. : 04 66 63 10 32
Mob. : 06 51 80 12 12

--- PyGate Linux v1.5.2
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On 14.01.2026 8:41, Nicolas Kovacs wrote:

Le 13/01/2026 … 17:15, Dan Ritter a ‚critÿ:

If you control the router/DNS/DHCP, then the best move is to
drop NetworkManager and use /etc/network/interfaces:

auto enp3s0
auto br0
iface br0 inet static
ÿÿÿÿbridge_ports enp3s0
ÿÿÿÿ address 192.168.2.3
ÿÿÿÿ netmask 255.255.255.0
ÿÿÿÿ gateway 192.168.2.1

I tried what you suggested, and I have a weird result. It works, but I
get an error message.

# ip -brief -family inet address show
loÿÿÿÿÿÿÿÿÿÿÿ?

?ÿÿ UNKNOWNÿÿÿÿÿÿÿ 127.0.0
.1/8

br0ÿÿÿÿÿÿÿÿÿÿÿ?

?ÿ UPÿÿÿÿÿÿÿÿÿÿ?
?ÿ 192.168.2.3/24

On startup there was a little hiccup with a little red error instead
of a green OK. So I checked, and here it is:

# journalctl -p err
...
Jan 14 08:37:35 sandbox systemd[1]: Failed to start networking.service
- Raise network interfaces.

Any idea what's causing this error message ?

Cheers,

Niki

Hi Niki,

That seems completely normal. I have checked 5 different Debian 13 installations, and they display the same with this command. Never
thought about it, as everything works. Note that UNKNOWN doesn't mean
that the interface is down. If the lo interface had been down, the
computer probably wouldn't have been working anyway.

Best regards,

Peter

Best

--- PyGate Linux v1.5.2
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)