Description of problem: Neutron ML2/OVS has the ability to define a global MTU and also to override it in every bridge mapping. In TripleO this is implemented as follows - NeutronGlobalPhysnetMtu (neutron::global_physnet_mtu) - NeutronML2PhysicalNetworkMtus (neutron::plugins::ml2::physical_network_mtus) The NeutronML2PhysicalNetworkMtus is especially useful for any operators using provider networks with a different MTU than the global one. Any operator using OVN will have 58 Bytes for the outer headers and Geneve encapsulation. So in order to have an overlay tenant networks with standard 1500 Bytes MTU, NeutronGlobalPhysnetMtu needs to be set at 1558. Due to OVN, at this point, it's not possible to globally override provider networks MTU size. So any provider network will have a weird mtu of 1558 bytes. The only workaround available is to create those specifying the desired MTU size. This introduces a change in the network creation workflow which for some operation could be a hard blocker adopting OVN. Version-Release number of selected component (if applicable): OSP13, OSP14, OSP15 How reproducible: Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info:
*** Bug 1809344 has been marked as a duplicate of this bug. ***
Verified on 13.0-RHEL-7/2020-05-28.2 with python-networking-ovn-4.0.4-6.el7ost.noarch. Tested on a virt environment with 9000 bytes MTU on bridges and all nodes interfaces. Configured the following settings: global_physnet_mtu=9000 in neutron.conf on all controllers path_mtu=1558 in ml2 section of ml2_conf.ini Note: I did not set physical_network_mtus because it needed for the case if we want to override global_physnet_mtu with a value that differs from global_physnet_mtu (it was tested in comment 17 and found working for provider network) Configured vlan 11 on the external bridge and also datacentre network to be vlan and no flat. Created vlan provider network as follows: Command: openstack network create --provider-physical-network datacentre --provider-network-type vlan --provider-segment 11 --external public Result: network with mtu 9000 was created Created tenant network (without specifying --mtu): Command: openstack network create internal_A Result: network with mtu 1500 created Performed also some sanity testing, created router, connected networks to the router, launched an instance, verified that the instance is accessible.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2020:2724