Cisco Nexus vPC port channel notes

Ran into an interesting issue with turning up vPC's between a Cisco Nexus 7010 and Cisco Nexus 5010's in regards to have the underlying port channels are configured. It turns out that if the 7k and 5k pairs have different port channel configurations they do not appropriately block the way you would think they should but instead continue to bounce the port. The mistake in my configuration was simple, the 5k was configured as such:
int e2/1
channel-group 10 mode active

int e2/2
channel-group 10 mode active

int p10
switchport mode trunk
vpc 10

The 7k was set as:
int e1/1
channel-group 10

int e1/2
channel-group 10

int p10
switchport mode trunk
vpc 10

The 5k was going LACP and the 7k was forced on. What was odd was that the vPC reported down as expected but the ports kept bouncing up and down which then forced spanning-tree to go into effect, not something I desired to have happen in this misconfiguration situation. I would have been ok with the port(s) staying down due to a port channel type mismatch but it kept trying to bring the ports up which was causing loops and causing spanning-tree to do its thing.

What I found interesting was that if I simply disabled one of the 7k ports, for instance int e1/2 everything would stabilize out since there was not a loop (no spanning tree) and the vPC still reported down. Expected behavior when you think about it but not intuitive when debugging the problem.

Once I corrected the port-channel configuration and forced everything on the vPC came up and I was able to fail interfaces with no interruption of traffic. My concern regarding this is the impact it had on all the vlans associated with that trunk, so it is critical to make sure that adding any new 5k's to the 7k's that the port configurations are double checked or an outage is possible due to this problem. I sort of wish the ports would error disable out due to vPC determining that the port channel type doesn't match to help prevent the L2 loop situation. This would keep the ports from bouncing and therefore prevent spanning-tree from having to go into effect to do loop prevention.
- Ed