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[Yang Li <yang.li@xxxxxxxxxxxx>]

** Changed in: neutron
       Status: Incomplete => Invalid

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https://bugs.launchpad.net/bugs/1845603

Title:
  multiple type networks with different mtu cause vm connectivity
  problem

Status in neutron:
  Invalid

Bug description:
  In my environment, vlan and vxlan are both exist, and their mtu is 1500 and 1450.
  I use vlan network to create a instance-A, and use vxlan network to create a instance-B, the instance-A and instance-B are in the same compute nodes.

  Then I found the mtu of br-int is 1450, this will cause
  instance-A'iperf result is 0 in , because instance-A's mtu 1500 is
  large than 1450.

  I did some investigation, found that the ovs bridge's mtu is decided
  by the minimum mtu tap device which belong to ovs bridge, for example,
  the instance-A's tap mtu is 1500, the instance-B's mtu is 1450, then
  br-int's mtu will be set to 1450 automatically.

  Seems the neutron doesn't support this scenario which vlan and vxlan
  both exist in ovs environment, I'm not sure if it's a bug.

  I have a workaround to solve this problem, use command "ovs-vsctl set
  int br-int mtu_request=1500", then the br-int will be always 1500, the
  instance-A's iperf program worked fine.

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