[openstack-dev] [nova][neutron][upgrade] Grenade multinode partial upgrade

Ihar Hrachyshka ihrachys at redhat.com
Tue Jan 12 12:01:21 UTC 2016

Clark Boylan <cboylan at sapwetik.org> wrote:

> On Mon, Jan 11, 2016, at 12:35 PM, Sean M. Collins wrote:
>> Nice find. I actually pushed a patch recently that we should be
>> advertising the MTU by default. I think this really shows that it should
>> be enabled by default.
>> https://review.openstack.org/263486l
> ++ Neutron should be able to determine what the outer MTU is and adjust
> the advertised inner MTU automatically based on the overhead required
> for whatever tunnel protocol is in use all without the deployer or cloud
> user needing to know anything special.

Let me clarify: there is still requirement for the image you boot to honour  
one of the ways we advertise MTU from neutron (DHCP MTU opton; RA for IPv6  
networks; …) Neutron cannot change mtu for the device that is seen from  
inside of the instance.

That said, most real images, including cirros since last year, should  
support the DHCP option.


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