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Description of problem: Starting Newton, global_physnet_mtu was supposed to be the single parameter that the user can change to change the mtu of the guest and all the interfaces leading to the guest. However, bumping global_physnet_mtu to 9000 and restarting neutron services changes MTU of all the virtual interfaces including tap, bridge, ports on ovs etc to 8946 but leaves the Tenant network VLAN interface to 1500 causing ping to work but ssh to guest fail. There should be a single parameter than can be changed during deploy/later like OvercloudBaseMTU : 1500 and everything should work from there. Version-Release number of selected component (if applicable): RHOP 10 How reproducible: 100% Steps to Reproduce: 1. Deploy overcloud 2. Now change global_physnet_mtu to 9000 3. All the virtual interfaces are set to 8946 but tenant vlan interface remains at 1500 breaking ssh access Actual results: Cannot SSH to gues Expected results: SSH should work and in fact network tests should report greater throughput Additional info:
ip a on the compute node: http://pastebin.test.redhat.com/423087 ovs-vsctl show on the compute node: http://pastebin.test.redhat.com/423088 You can see how qvo98d4949e-33@qvb98d4949e-33, qvb98d4949e-33@qvo98d4949e-33 and tap98d4949e-33 are all set to 8946 but vlan237 is set to 1500
From the Launchpad bug: "Fwiw, manually bumping the tenant network vlan interface to 9000 solves the issue and I'm able to SSH to the guest." From comment 1 Sai is talking about "vlan237", an OVS internal port created by TripleO. Seems like a straight forward bug, although not a regression, this functionality has simply never worked as far as I know.
NeutronGlobalPhysnetMtu is neutron specific. This bug is effectively an RFE for a value that configures neutron as well as any interfaces that might be involved with traffic where the neutron global_physnet_mtu holds sway. We will need to file a blueprint u/s for this. While we can target rocky there are other priorities that may take precedent and it may be pushed further out.
Declaring this WONTFIX with Brent's concurrence.