Cloud instance with reduced MTU, container uses 1500, connections stall

Andreas Hasenack andreas at
Fri Jun 13 20:01:53 UTC 2014


I'm not sure where or how this should be fixed.

I have a case where openstack was juju deployed with neutron networking,
and we needed to set instance-mtu = 1454 in the neutron-gateway charm.

Instances launched in the cloud get that 1454 MTU set in their eth0 devices
and life is good.

If, however, I create a container inside an instance (for example, via juju
deploy --to lxc:0), that container gets eth0 set with an MTU of 1500. And
that makes almost all connections stall, and the deployment fails.

Now, who should set the default MTU for containers to be 1454 in this case?
Or, more explicitly, to mimic the MTU of the "host" (in this case, the
instance)? juju? lxc-create?
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