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Hi Neil,

Thanks.
The ip route output is as following, i guess the 0.0.0.0 gateway is only
listed by cloud-init:

debian at instance:/$ ip route
default via 192.168.10.1 dev eth0
192.168.10.0/24 dev eth0  scope link
169.254.169.254 via 192.168.10.1 dev eth0
192.168.11.0/24 dev eth0  scope link
192.168.12.0/24 dev eth0  proto kernel  scope link  src 192.168.10.2

(ip addresses are altered for security reasons).

I'm not sure what creates these routes. I have two suspects: cloud-init and
DHCP. As the same issue is observed on instances without cloud-init this
rules out cloud-init.
We see the same issue on both Windows and Linux instances.

We do not have host routes in the subnet config.

Thanks,
Remco.

On Fri, Apr 22, 2016 at 12:06 PM, Neil Jerram <Neil.Jerram at metaswitch.com>
wrote:

> On 22/04/16 10:59, Remco wrote:
> > Hi,
>
> Hi Remco,
>
> > We are running Liberty, with provider networks. We use the Neutron DHCP
> > agent to configure IPv4 and IPv6 addresses for instances. This is all
> > working great, however we sometimes need to put multiple subnets on one
> > VLAN interface (for legacy reasons). This is in fact also working,
> > however it configures some unwanted routes.
> >
> > For example, the following subnets exist in a Neutron network:
> >
> > 192.168.10.0/24 <http://192.168.10.0/24>
> > 192.168.11.0/24 <http://192.168.11.0/24>
> > 192.168.12.0/24 <http://192.168.12.0/24>
> >
> > I.e. if the IP address obtained is 192.168.10.8/24
> > <http://192.168.10.8/24>, the following routes are inserted:
>
> Do you mean on the instance?
>
> > 192.168.10.0/24 <http://192.168.10.0/24> with gateway 0.0.0.0
> > 192.168.11.0/24 <http://192.168.11.0/24> with gateway 0.0.0.0
> > 192.168.12.0/24 <http://192.168.12.0/24> with gateway 0.0.0.0
>
> Does 'with gateway 0.0.0.0' mean directly connected?  What precisely
> does 'ip r' show?
>
> (I've never seen, e.g., '192.168.10.0/24 via 0.0.0.0' before, and don't
> know how I would interpret that.  So guessing you mean '192.168.10.0/24
> dev eth0'.)
>
> > The first route is obviously not an issue, as this route is directly
> > connected, but the other routes are plain wrong and stop traffic from
> > being routed to the default gateway.
> >
> > Does anyone know how to disable this behavior? I only want a default
> > gateway obtained from DHCP and I do not need any further routes.
>
> Do you know what is creating the .11 and .12 routes?  Unless you have
> host routes in your subnet config, I would expect the instance only to
> create a route for its DHCP-issued address, and hence only for .10.
>
>         Neil
>
>
>
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