Comment 5 for bug 1754036

Thanks for the suggestion! I think we're using 1350...

https://github.com/openstack/tripleo-quickstart-extras/blob/master/config/environments/rdocloud.yml#L34

https://logs.rdoproject.org/openstack-periodic/periodic-tripleo-ci-centos-7-ovb-1ctlr_1comp-featureset020-master/a049ff7/undercloud/home/jenkins/overcloud_network_params.yaml.txt.gz

```
# Defines overcloud network parameters based on parameters given.

parameter_defaults:
  NeutronGlobalPhysnetMtu: 1350
```

but an initial look at the ifcfg files from OC controller doesn't show the MTU setting. I'll look into this tomorrow morning to see if we're setting it dynamically but not persisting (guessing this is the case?)