Debian 10 bridge disappear after reboot

Question

I created a bridge in my Debian 10 router like this # brctl addbr br0 after that I add network interface on my bridge # brctl addif br0 eno1

brctl show
bridge name bridge id       STP enabled interfaces
br0     8000.0030bdb2810d   no      eno1

My /etc/network/interfaces look like this

# The loopback network interface
auto lo
iface lo inet loopback

# Set up interfaces manually, avoiding conflicts with, e.g., network manager

iface eno1 inet manual

# Bridge setup
auto br0

iface br0 inet dhcp
      bridge_ports eno1

Everything works well, but If I reboot my router, brctl show returns empty result. In my syslog I have this strange line : bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if youd nedd this is that normal ? PS : I disabled ipv6 in sysctl.conf with this line net.ipv6.conf.all.disable_ipv6 = 1

What I need to do to have my bridge when my router reboot?

Answer 1

The Debian wiki mentions what may be the same problem, for Stretch and Buster. If your system has the file /etc/network/interfaces.d/setup (mine does not) you could try removing it.

Otherwise, I like your idea of adding the bridge on startup. You could try in /etc/network/interfaces:

auto br0
iface br0 inet dhcp
  pre-up brctl addbr br0 && brctl addif br0 eno1
  post-down brctl delif br0 eno1 && brctl delbr br0

The post-down line is included for symmetry and to make sure that the pre-up line doesn't fail (which would abort ifup br0) if br0 is ever taken down and back up.

A safer way is probably:

auto br0
iface br0 inet dhcp
  pre-up { brctl addbr br0 && brctl addif br0 eno1; } || true

where the || true prevents the pre-up command from ever failing and aborting ifup br0. Ref: https://manpages.debian.org/buster/ifupdown/interfaces.5.en.html

I don't think you need to worry about the arp/ip/ip6tables filtering warning you're seeing, unless you need such filtering. The warning is unrelated to your current problem.