TP-Link T2600G-18TSTL-SG3216 T2600G-18TSUN V1 Configuration Guide - Page 324

Configuring Spanning Tree Figure 1-4 MST Region A Spanning Tree 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, which is a special MST instance with an instance ID of 0. By default, all the VLANs are mapped to IST. CST The Common Spanning Tree, which is the spanning tree connects 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, comprising IST and CST, 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. »» Loop Protect Loop Protect function is used to prevent loops caused by link congestions or link failures. It is recommended to enable this function on root ports and alternate ports. Configuration Guide 294