Comment 3 for bug 1776228

Hi Daniel,
for the moment I reverted to static configuration for all but the primary NIC.
It is currently the only reliable setup, as systemd DHCP seems to add redundand default routes intermittently when UseRoutes is disabled.
Not ideal, but the reqired stopgap.
Cheers!Michael
-------- Ursprüngliche Nachricht --------Von: Daniel Axtens <email address hidden> Datum: 23.07.18 05:01 (GMT+01:00) An: <email address hidden> Betreff: [Bug 1776228] Re: Duplicate default routes on VMs with multiple NICs
Hi,

It looks like we'd need to implement support for: (from systemd.network)

UseDNS=
UseNTP=
UseHostname=
UseDomains=
UseRoutes=

to get you at least some of the functionality you had.

I wonder if in the shorter term we could implement route metric support
as discussed in LP: #1771834. That seems to contemplate a similar
scenario (multiple interfaces with DHCP). Would that be a workable stop-
gap for you?

Regards,
Daniel

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Title:
  Duplicate default routes on VMs with multiple NICs

Status in netplan:
  New

Bug description:
  I'm facing issues with OpenStack VMs built from Ubuntu 18.04 cloud
  image and configured with multiple NICs. I have a solution working on
  16.04, which doesn't do any more since the introduction of netplan.

  Requirements:

   - Multiple interfaces connected to different networks.
   - All NICs configured via DHCP to ensure IP address, but also parameters like MTU adapt to the environment automatically.
   - Default route is supposed to use one specific NIC and network.

  The solution on 16.04 was customization of /etc/dhcp/dhclient.conf,
  such that all unique parameters are retrieved from only that
  interface. Example with ens3 being the intended authoritative
  interface:

    option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;
    send host-name = gethostname();
    request subnet-mask, broadcast-address, time-offset,
            netbios-name-servers, netbios-scope, interface-mtu,
            rfc3442-classless-static-routes;
    interface "ens3" { request routers, domain-name, domain-name-servers, domain-search, host-name,
                       dhcp6.name-servers, dhcp6.domain-search, dhcp6.fqdn, dhcp6.sntp-servers, ntp-servers; }

  This does no longer work with netplan. I couldn't figure any netplan
  properties to configure DHCP client to that granularity. And
  /etc/dhcp/dhclient.conf no longer seems to be honored. As I can see in
  VM startup console log, each interface is getting default route
  assigned and the system remains unresponsive most of the times.

  How am I supposed to solve this on a netplan managed system?

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