User`s manual

Port Information: You can see port Role, Port State, Path Cost, Port Priority, Oper

P2P mode, Oper edge port mode and Aggregated (ID/Type).

4.4.4 MSTP (Multiple Spanning Tree Protocol) Configuration

MSTP is the abbreviation of Multiple Spanning Tree Protocol. This protocol is a

direct extension of RSTP. It can provide an independent spanning tree for

different VLANs. It simplifies network management, provides for even faster

convergence than RSTP by limiting the size of each region, and prevents VLAN

members from being segmented from the rest of the group (as sometimes occurs

with IEEE 802.1D STP).

While using MSTP, there are some new concepts of network architecture. A

switch may belong to different groups, act as root or designate switch, generate

BPDU for the network to maintain the forwarding table of the spanning tree.

With MSTP can also provide multiple forwarding paths and enable load balancing.

Understand the architecture allows you to maintain the correct spanning tree

and operate effectively.

One VLAN can be mapped to a Multiple Spanning Tree Instance (MSTI). The

maximum Instance Switch supports is 16, range from 0-15. The MSTP builds a

separate Multiple Spanning Tree (MST) for each instance to maintain connectivity

among each of the assigned VLAN groups. An Internal Spanning Tree (IST) is used

to connect all the MSTP switches within an MST region. An MST Region may

contain multiple MSTP Instances.

The figure shows there are 2 VLANs/MSTP Instances and each instance has its

Root and forwarding paths.

A Common Spanning Tree (CST) interconnects all adjacent MST regions and acts

as a virtual bridge node for communications with STP or RSTP nodes in the global

network. MSTP connects all bridges and LAN segments with a single Common

and Internal Spanning Tree (CIST). The CIST is formed as a result of the running

spanning tree algorithm between switches that support the STP, RSTP, MSTP

protocols.

The figure shows the CST large network. In this network, a Region may has

different instances and its own forwarding path and table, however, it acts as a

single Bridge of CST.