Comment 0 for bug 1736975

Configuring "/etc/netplan/01-netcfg.yaml" with an anonymous bridge seems to require running "ip link set dev br0 up" to bring the bridge up after boot. A bridge configured with an IP address is automatically up after boot.

This is only a problem if you want an anonymous bridge which comes up automatically after boot. For example, if you preferred to isolate host traffic from your autostarting virtual machine traffic.

Configuration that results in the bridge being down after boot:
network:
  version: 2
  renderer: networkd
  ethernets:
    enp22s2:
      dhcp4: yes
    enp22s3:
      dhcp4: no
  bridges:
    br0:
      interfaces: [enp22s3]
      dhcp4: false
      parameters:
        stp: false
        forward-delay: 0

Enabling DHCP results in a bridge that is automatically up after boot:
network:
  version: 2
  renderer: networkd
  ethernets:
    enp22s2:
      dhcp4: yes
    enp22s3:
      dhcp4: no
  bridges:
    br0:
      interfaces: [enp22s3]
      dhcp4: true
      parameters:
        stp: false
        forward-delay: 0

Setting a static IP address results in a bridge that is automatically up after boot:
network:
  version: 2
  renderer: networkd
  ethernets:
    enp22s2:
      dhcp4: yes
    enp22s3:
      dhcp4: no
  bridges:
    br0:
      interfaces: [enp22s3]
      dhcp4: false
      addresses: [192.168.1.100/24]
      parameters:
        stp: false
        forward-delay: 0

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: nplan 0.30
ProcVersionSignature: Ubuntu 4.13.0-17.20-generic 4.13.8
Uname: Linux 4.13.0-17-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.5
Architecture: amd64
Date: Thu Dec 7 11:06:25 2017
ProcEnviron:
 LANGUAGE=en_CA:en
 TERM=screen
 PATH=(custom, no user)
 LANG=en_CA.UTF-8
 SHELL=/bin/bash
SourcePackage: nplan
UpgradeStatus: No upgrade log present (probably fresh install)