TL-SL3428_V3_User_Guide - TP-Link

Figure 7-2 Basic MSTP diagram‣ MSTPMSTP divides a network into several MST regions. The CST is generated between these MSTregions, and multiple spanning trees can be generated in each MST region. Each spanning tressis called an instance. As well as STP, MSTP uses BPDUs to generate spanning tree. The onlydifference is that the BPDU for MSTP carry the MSTP configuration information on the switches.‣ Port StatesIn an MSTP, ports can be in the following four states:• Forwarding: In this status the port can receive/forward data, receive/send BPDU packets aswell as learn MAC address.• Learning: In this status the port can receive/send BPDU packets and learn MAC address.• Blocking: In this status the port can only receive BPDU packets.• Disconnected: In this status the port is not participating in the STP.‣ Port RolesIn an MSTP, the following roles exist:• Root Port: Indicates the port that has the lowest path cost from this bridge to the Root Bridgeand forwards packets to the root.• Designated Port: Indicates the port that forwards packets to a downstream network segmentor switch.• Master Port: Indicates the port that connects a MST region to the common root. The pathfrom the master port to the common root is the shortest path between this MST region andthe common root.• Alternate Port: Indicates the port that can be a backup port of a root or master port.• Backup Port: Indicates the port that is the backup port of a designated port.• Disabled: Indicates the port that is not participating in the STP.The following diagram shows the different port roles.73