[openstack-dev] [neutron] network_device_mtu is not applied to VMs

Elena Ezhova eezhova at mirantis.com
Mon Aug 4 14:03:14 UTC 2014


Hi!

I feel I need a piece of advice regarding this bug [1].

The gist of the problem is that although there is an option
network_device_mtu that can be specified in neutron.conf VMs are not
getting that mtu on their interfaces. MTU can be specified by the dhcp
agent by adding the option to dnsmasq_config_file like it’s done here [2].
So one of the solutions might be to check whether the network_device_mtu is
specified during spawning of Dnsmasq process and if it is add an option to
Dnsmasq options file.

But I am not sure whether this is something worth being fixed and if the
above-described option is the right way to fix the bug.

By the way, as I found out, MTU cannot currently be set for instances that
are running cirros, because cirros does not handle dhcp options like it’s
said in the following bug. [3]

Regards, Elena Ezhova

[1] https://bugs.launchpad.net/neutron/+bug/1348788

[2]
https://ask.openstack.org/en/question/12499/forcing-mtu-to-1400-via-etcneutrondnsmasq-neutronconf-per-daniels/

[3] https://bugs.launchpad.net/cirros/+bug/1301958
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