Terms and Acronyms

• alternate port (RSTP and MSTP only)—This port provides an alternate path toward the root bridge should the root port or the path from the root port become unavailable.
• backup port (RSTP and MSTP only)—This port provides a backup path to the leafs of the spanning tree should the designated port become unavailable.
• bridge domain—A set of logical ports that share the same flooding or broadcast characteristics. As in a virtual LAN, a bridge domain spans one or more ports of multiple devices. By default, each bridge domain maintains its own forwarding database of MAC addresses learned from packets received on ports belonging to that bridge domain. See also broadcast domain and VLAN.
• designated port—Port that provides the shortest path connection to the root bridge for the attached LAN segment.
• integrated routing and bridging (IRB) interface—Interface that defines all Layer 3 protocol families (inet, mpls, and so on) that are to be used for routing.
• learning domain—Layer 2 forwarding database that contains MAC addresses. Learning domains are associated with one bridge domain, and there can be multiple learning domains within one bridge domain.
• master port—Port that is the best path to reach the CST root bridge from any MST region.
• Multiple Instances Spanning Tree Protocol—Loop prevention protocol originally defined in IEEE 802.1s, but now part of IEEE 802.1Q. MSTP is backward-compatible with STP and RSTP.
• Rapid Spanning Tree Protocol—Loop prevention protocol defined in IEEE 802.1w and now part of IEEE 802.1D. It allows for faster convergence time than STP. RSTP is backward-compatible with STP.
• Spanning Tree Protocol—Loop prevention protocol defined in IEEE 802.1D.
• virtual switch—Routing instance which can contain multiple bridge domains and which runs multiple Layer 2 loop prevention protocols and Layer 3 routing protocols. A port can belong to only one virtual switch if Layer 2 loop prevention protocols are to be implemented on this port.
• vlan-id—VLAN tag for data switched within a single bridge domain.