On Wed, May 17, 2017 at 10:03 AM, Mathieu Gagné <[email protected]> wrote: > Hi, > > When you attach multiple networks/interfaces to an instance and at > least 2 subnets have a default route, you end up with 2 default routes > in network_data.json. > > If cloud-init or any other in-guest agent is used to configure the > network, you could end up with 2 default routes and to an extend, with > non-working networking. (like we found out recently) > > How should we handle this situation where you could end up with 2 > subnets, each having a default route? > > * Should Nova decide which default route to expose to the instance? > * Should the in-guest agent pick one? > > I'm looking for opinions and advises on how to fix this issue. >
I would also like to draw attention to a spec I wrote which faces the same questions and challenges related to multiple fixed-ips per port support: https://review.openstack.org/#/c/312626/7 Quoting the commit message here: > Each subnet can have its own routes and default route which create challenges: > * Should all routes be merged in the same "routes" attribute? > * What should be the default route if more than one subnet provides a default route? Should we provide all of them? > * What should be the implementation logic an in-guest agent use to determine the default route? > * Are there use cases where one default route should be used over the others? I'm thinking about NFV or other specialized use cases. -- Mathieu
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