If you're using openshift-ansible to deploy, you can set

openshift_node_sdn_mtu=1500

in your inventory and run the deployment. That should fix it up. I'm not
100% sure it will adjust the MTU of docker's bridge though. It depends how
you deployed it. Look for DOCKER_NETWORK_OPTIONS= in your startup files,
make sure that got changed, and restart docker. Mine is
in /etc/sysconfig/docker-network.

Also remember if you're running OVS or something else using tunneling,
you'll need the MTU of docker and the SDN to be lower (1400 probably) to
allow for the encapsulation.

-Erik

On Tue, Aug 27, 2019 at 12:36 PM Samuel Martín Moro <[email protected]>
wrote:

> Look at the ConfigMaps in project openshift-node.
> Change the mtu param in there first.
> Restart the node (origin-node / atomic-openshift-node) service on all
> nodes.
> If all goes well, you should be able to then reconfigure your network
> interfaces.
>
> On Tue, Aug 27, 2019, 6:32 PM Tim Dudgeon <[email protected]> wrote:
>
>> OK, thanks. So what would be needed to change this on a running system
>> rather than when you first install openshift?
>> On 27/08/2019 17:14, Brian Jarvis wrote:
>>
>> Tim,
>>
>> You need to set the MTU of the OpenShift SDN to be lower than the MTU of
>> the NIC.
>>
>> This is described in
>> https://docs.openshift.com/container-platform/3.11/scaling_performance/network_optimization.html#scaling-performance-optimizing-mtu
>> .
>>
>>
>>
>>
>> On Tue, Aug 27, 2019 at 12:02 PM Tim Dudgeon <[email protected]>
>> wrote:
>>
>>> In one of our OKD3.11 environments the hosting provider wanting to
>>> change the network MTU from 9000 to 1500 and did that for all the
>>> physical network interfaces of all the nodes.
>>>
>>> This caused the Openshift networking to break completely. Resetting back
>>> to 9000 restored things.
>>>
>>> Is there a way to allow for this to be done on a running Openshift
>>> system?
>>>
>>> Thanks
>>> Tim
>>>
>>> _______________________________________________
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>>>
>>
>>
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