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Hi Ageeleshwar,

I guess I just asked similar question yesterday.

But, I'm not understand what you mean "when your ethernet is limited to 1500".

Not sure if we're talking at the right direction.
Anyway, here is what I know:

This is based on if you're using neutron + ovs.


1.       Configure /etc/neutron/plugins/openvswitch/ovs_neutron_plugin.ini

veth_mtu = ${your_MTU}



If you're using gre/vxlan, this configure can be ignored.



2.       Configure /etc/nova/nova.conf

network_device_mtu= ${your_MTU}



But this may not work due to bug https://bugs.launchpad.net/nova/+bug/1260697.

Unless you apply the fix patch.



3.       Configure /etc/neutron/ dhcp_agent.ini

dnsmasq_config_file = /etc/neutron/dnsmasq-neutron.conf



And add to /etc/neutron/dnsmasq-neutron.conf:

dhcp-option-force=26,${your_MTU}


I'm working under CentOS 6.4+ Havana + OVS + GRE.
And I just tested it, It works fine to me.
I have configured MTU=8500 in all configure files, while the physical NIC used for OVS (local IP) is using MTU=9000.

Thanks.
-chen

From: Ageeleshwar Kandavelu [mailto:Ageeleshwar.Kandavelu at csscorp.com]
Sent: Monday, January 27, 2014 9:57 PM
To: Li, Chen
Cc: openstack at lists.openstack.org
Subject: [Openstack] How to enable jumbo frames for instances

Hi,
Is it possible to have a higher MTU when your ethernet is limited to 1500?

Thank you,
Ageeleshwar K
http://www.csscorp.com/common/email-disclaimer.php
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