You have created a network design that has two point-to-point Metro Ethernet circuits extending a single production VLAN between two data centers. Under normal circumstances, one circuit will carry tr

EtherChannel (802.3ad LACP or PAgP) combines the two Metro Ethernet circuits into a single logical link, allowing STP to see one path instead of two and enabling both physical circuits to carry traffic simultaneously through load balancing.

MST reduces STP instance overhead by mapping multiple VLANs to fewer instances, but it still enforces one blocking port per instance and does not allow both circuits to forward traffic for the same VLAN simultaneously.

Multichassis EtherChannel (such as Cisco vPC or VSS) is required when the two circuits terminate on different physical switches at one or both ends, allowing the EtherChannel bundle to span multiple chassis so both links remain active without STP blocking one.

PVST+ runs a separate STP instance per VLAN and can load-balance VLANs across different links, but it still blocks one redundant port per VLAN per topology and cannot make both circuits active for a single production VLAN.