TP-Link T1600G-28PS Jetstream Smart Switches User Guide - Page 326

Configuring Spanning Tree Spanning Tree MST Instance The MST instance is a spanning tree running in the MST region. Multiple MST instances can be established in one MST region and they are independent of each other. As is shown in Figure 1-4, there are three instances in a region, and each instance has its own root bridge. Figure 1-4 MST Region A B C Instance 1 (root bridge: A) VLAN 3 Instance 1 Instance 2 (root bridge: B) VLAN 4-5 IST (root bridge: C) Other VLANs Instance 2 IST Blocked port VLAN-Instance Mapping VLAN-Instance Mapping describes the mapping relationship between VLANs and instances. Multiple VLANs can be mapped to a same instance, but one VLAN can be mapped to only one instance. As Figure 1-4 shows, VLAN 3 is mapped to instance 1, VLAN 4 and VLAN 5 are mapped to instance 2, the other VLANs are mapped to the IST. IST The Internal Spanning Tree (IST), which is a special MST instance with an instance ID 0. By default, all the VLANs are mapped to IST. CST The Common Spanning Tree (CST), that is the spanning tree connecting all MST regions. As is shown in Figure 1-3, region1-region 4 are connected by the CST. CIST The Common and Internal Spanning Tree (CIST), comprising IST and CST. CIST is the spanning tree that connects all the switches in the network. 1.3 STP Security STP Security prevents the loops caused by wrong configurations or BPDU attacks. It contains Loop Protect, Root Protect, BPDU Protect, BPDU Filter and TC Protect functions. User Guide 301