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[Ian Kumlien <1745150@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

If you run neutron with OVS it doesn't honor MTU values, which is a
issue if you host external environments that needs to communicate with
other entities that f.ex. have PMTU disabled as a security measure...

Another issue is that the MTU difference happens on a L2 bridge and
packets will thus be dropped on the floor and noone will clean up the
mess =)

Looking at:
http://docs.openvswitch.org/en/latest/faq/issues/

Which states:
Q: How can I configure the bridge internal interface MTU? Why does Open vSwitch keep changing internal ports MTU?
...
ovs-vsctl set int br0 mtu_request=1450
...
---

I can find no reference to this happening anywhere in the code - every
where i've looked MTU seems to have been completely ignored.

We've been trying to migrated away from OVS due to this, but it's a bit
more complex - we found the issue on linuxbridging and could mitigate
it, see https://bugs.launchpad.net/neutron/+bug/1744101

** Affects: neutron
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1745150

Title:
  neutron doesn't set MTU on ovs

Status in neutron:
  New

Bug description:
  If you run neutron with OVS it doesn't honor MTU values, which is a
  issue if you host external environments that needs to communicate with
  other entities that f.ex. have PMTU disabled as a security measure...

  Another issue is that the MTU difference happens on a L2 bridge and
  packets will thus be dropped on the floor and noone will clean up the
  mess =)

  Looking at:
  http://docs.openvswitch.org/en/latest/faq/issues/

  Which states:
  Q: How can I configure the bridge internal interface MTU? Why does Open vSwitch keep changing internal ports MTU?
  ...
  ovs-vsctl set int br0 mtu_request=1450
  ...
  ---

  I can find no reference to this happening anywhere in the code - every
  where i've looked MTU seems to have been completely ignored.

  We've been trying to migrated away from OVS due to this, but it's a
  bit more complex - we found the issue on linuxbridging and could
  mitigate it, see https://bugs.launchpad.net/neutron/+bug/1744101

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