A bridged communications network includes source routing transparent (SRT) bridges which forward frames that are structured in accordance with a source routing architecture and frames that are structured in accordance with a transparent bridging architecture. Each SRT bridge examines a received frame to determine its type. If the frame is a bridge protocol data unit (BPDU) frame, it is used to set the bridge in a forwarding or blocking state. Any non-BPDU which carries a routing information indicator (RII) bit set to a logical "1" are processed by a source routing function device which is provided in the SRT bridge. If the RII bit is set to logical "0", the frame is processed by a transparent bridge function device which is also provided in the SRT bridge.