how to make sure bridge interface is up with netplan after reboot

[Tom H]

On Fri, Mar 9, 2018 at 3:59 PM, mabi via ubuntu-users
<ubuntu-users at lists.ubuntu.com> wrote:
> On March 9, 2018 7:19 PM, Tom H <tomh0665 at gmail.com> wrote:
>> On Fri, Mar 9, 2018 at 10:34 AM, mabi via ubuntu-users
>> ubuntu-users at lists.ubuntu.com wrote:
>>>
>>> I am using Ubuntu 17.10 and therefore Netplan which I have configured
>>>
>>> a bridge for a specific network interface for my Xen virtual machines.
>>>
>>> Unfortunately when I reboot the server that bridge interface is in
>>>
>>> state DOWN so that I have to manually set it up using "ip link set
>>>
>>> xenbr1 up" command. Now does anyone know how to make sure netplan
>>>
>>> brings my bridge interface automatically up at reboot?
>>>
>>> Here is the relevant part of my netplan netcfg.yaml file:
>>>
>>> network:
>>> version: 2
>>> renderer: networkd
>>> ethernets:
>>> eno3:
>>> dhcp4: no
>>> bridges:
>>> xenbr1:
>>> interfaces: \[eno3\]
>>> dhcp4: no
>>> parameters:
>>> stp: no
>>> forward-delay: 0
>>
>> You have "dhcp4: no" and no "addresses:" defined so I wouldn't expect
>> xenbr1 to be "UP".
>>
>> What do the "*.network" files in "/run/systemd/" contain?
>
> That's correct I have no IP addresses defined on my xenbr1 bridge
> because it is just a bridge between my Xen virtual machines which are
> hooked up to this bridge and a hardware firewall which is connected
> onto the eno3 physical NIC. Both VM and firewall have an IP address
> but not the bridge. So it looks like this:
>
> [VM(eth0)]-----[(xenbr1)XenHypervisor(eno3)]-----[(eth0)Firewall(eth1)]-----[Internet]
>
> As far as I am concerned the xenbr1 bridge interface on my Xen
> hypervisor does not need any IP address, there is no purpose for it
> having an IP address.
>
> In the /run/systemd/network directory there is no xenbr1.network file
> but there is a eno3.network file with the following content:
>
> [Match]
> Name=eno3
>
> [Network]
> Bridge=xenbr1
> LinkLocalAddressing=no
> IPv6AcceptRA=no

If you assign "0.0.0.0/0" to xenbr1, there should be a xenbr1
".network" file in "/run/systemd/network/" to go with the xenbr1
".netdev" one and xenbr1'll be brought up. Untested, so I hope!