When the Peer-Switch feature is enabled on a Cisco vPC domain, it broadcasts the same BPDUs from both vPC primary and secondary nodes to peer devices. But a VCS on a VLAG assumes that any logical interface receives only one BPDU from any of its member ports, so when it receives the two BPDUs from a Cisco vPC domain it creates a churn of VLAG mastership, and this increases the CPU load on a Extreme VDX. To avoid these problem, BDPUs received on the VLAG non-master are dropped. When the Peer-Switch functionality is enabled and the the VLAG Master is selected, BPDUs received on VLAG Non-Master are dropped unless there is a change in the status of the VLAG Master.
<interface xmlns="urn:brocade.com:mgmt:brocade-interface"> <ethernet> <name>2/1</name> <spanning-tree xmlns="urn:brocade.com:mgmt:brocade-xstp"> <peer-switch></peer-switch> </spanning-tree> </ethernet> </interface>