Question

A data center engineer configures a vPC domain between two Nexus 9000 switches. After bringing up the vPC, several vPC member ports remain down, and 'show vpc consistency-parameters' reveals a mismatch in the STP MST region configuration between the peers. However, a separate mismatch in the allowed VLAN list on a different vPC only generated a syslog warning while keeping that vPC operational. What explains the difference in behavior between these two mismatches?

Accepted Answer

The MST region is a Type 1 consistency parameter, which suspends the vPC on mismatch, while the allowed VLAN list is a Type 2 parameter, which only logs a warning and keeps forwarding on consistent VLANs

Answer

The MST region is a Type 2 consistency parameter that suspends the vPC, while the allowed VLAN list is a Type 1 parameter that only warns

Answer

Both are Type 1 parameters, but the MST mismatch triggered a peer-link flap that brought the vPC down independently of consistency checking

Answer

The MST region mismatch disabled the vPC because it is a global parameter, whereas the allowed VLAN list is checked only during graceful consistency check and is always ignored