[Bug 1742505] Update Released
1742505 at bugs.launchpad.net
Wed Feb 21 14:44:16 UTC 2018
The verification of the Stable Release Update for openvswitch has
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gre_sys set to default 1472 when using path_mtu > 1500 with ovs 2.8.x
Status in Ubuntu Cloud Archive:
Status in Ubuntu Cloud Archive pike series:
Status in Ubuntu Cloud Archive queens series:
Status in neutron:
Status in linux package in Ubuntu:
Status in openvswitch package in Ubuntu:
Status in linux source package in Artful:
Status in openvswitch source package in Artful:
Status in linux source package in Bionic:
Status in openvswitch source package in Bionic:
OpenStack Clouds using GRE overlay tunnels with > 1500 MTU's will observe packet fragmentation/networking issues for traffic in overlay networks.
Deploy OpenStack Pike (xenial + pike UCA or artful)
Create tenant networks using GRE segmentation
Instance networking will be broken/slow
gre_sys devices will be set to mtu=1472 on hypervisor hosts.
Minimal; the fix to OVS works around an issue for GRE tunnel port setup via rtnetlink by performing a second request once the gre device is setup to set the MTU to a high value (65000).
[Original Bug Report]
Pike neutron 11.0.2-0ubuntu1.1~cloud0
Jumbo frames setttings per: https://docs.openstack.org/mitaka/networking-guide/config-mtu.html
global_physnet_mtu = 9000
path_mtu = 9000
gre_sys MTU is 1472
Instances with MTUs > 1500 fail to communicate across GRE
ifconfig gre_sys MTU 9000
Note: When ovs rebuilds tunnels, such as on a restart, gre_sys MTU is set back to default 1472.
Note: downgrading from OVS 2.8.0 to 2.6.1 resolves the issue.
With Ocata or Pike and OVS 2.6.x
gre_sys MTU defaults to 65490
It remains at 65490 through restarts.
This may be related to some combination of the following changes in OVS which seem to imply MTUs must be set in the ovs database for tunnel interfaces and patches:
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