1-10z MSTP supports mapping VLANs to spanning tree instances by means of a VLAN-to-instancemapping table. MSTP can reduce communication overheads and resource usage by mappingmultiple VLANs to one instance.z MSTP divides a switched network into multiple regions, each containing multiple spanning treesthat are independent of one another.z MSTP prunes a loop network into a loop-free tree, thus avoiding proliferation and endless cycling ofpackets in a loop network. In addition, it provides multiple redundant paths for data forwarding, thussupporting load balancing of VLAN data.z MSTP is compatible with STP and RSTP.Basic Concepts in MSTPFigure 1-4 Basic concepts in MSTPCSTRegion A0VLAN 1 mapped to instance 1VLAN 2 mapped to instance 2Other VLANs mapped to CISTRegion B0VLAN 1 mapped to instance 1VLAN 2 mapped to instance 2Other VLANs mapped to CISTRegion C0VLAN 1 mapped to instance 1VLAN 2 and 3 mapped toinstance 2Other VLANs mapped to CISTRegion D0VLAN 1 mapped to instance 1,B as regional root bridgeVLAN 2 mapped to instance 2,C as regional root bridgeOther VLANs mapped to CISTBPDU BPDUBPDUCDBAAssume that all devices in Figure 1-4 are running MSTP. This section explains some basic concepts ofMSTP.MST regionA multiple spanning tree region (MST region) consists of multiple devices in a switched network and thenetwork segments among them. These devices have the following characteristics:z All are MSTP-enabled,z They have the same region name,z They have the same VLAN-to-instance mapping configuration,
