ML2 Nexus MD does not appear to configure multiple switches

[Robert Starmer]

There is already a bug to add unit tests for multi-switch configuration, but there already appears to be a bug in that multiple switches can be defined in the configuration file, but multiple switches are not configured. The related bug is here:

https://bugs.launchpad.net/neutron/+bug/1330598

The issue is:

If you configure the Cisco Nexus ML2 MD with two switches that have the same target hypervisor ID, as in:

[ml2_mech_cisco_nexus_1:1.1.1.1]
compute-1=1/2

[ml2_mech_cisco_nexus_2:1.1.1.2]
compute-1=1/2

The system will only configure a VLAN on interface 1/2 on ml2_mech_cisco_nexus_1.

In addition it appears that the system will only ever configure devices on the first switch that is discovered.

Also, it does not appear possible to define port-channels as the target for these configurations, which breaks the use of virtual port-channel as a configured mechanism.

[Rich Curran (rcurran)]

The multi-switch support was added in Juno-1 via https://bugs.launchpad.net/neutron/+bug/1294900
Review: https://review.openstack.org/#/c/83546/