Which solution provides an active/active alternative to spanning-tree?

RSTP (Rapid Spanning Tree Protocol) still elects a root bridge and blocks redundant ports to prevent loops, making it an active/standby technology rather than a true active/active solution.

TRILL uses the IS-IS routing protocol to compute loop-free, equal-cost multipath routes across a Layer 2 network, enabling all links to forward traffic simultaneously without blocking redundant ports. Unlike spanning tree, TRILL encapsulates Ethernet frames with a TRILL header and distributes forwarding across multiple active paths, achieving genuine active/active operation with load balancing across the fabric.

MST (Multiple Spanning Tree) maps multiple VLANs to fewer spanning tree instances to improve load distribution but still relies on port blocking within each instance, so it is not a true active/active solution.

Ethernet Ring Protection Switching (ERPS/G.8032) is designed specifically for ring topologies and maintains loop-free operation by keeping one link blocked, which is an active/standby approach.