Allied Telesis AT-S60 - Manual (Page 213)

Chapter 12: STP, RSTP, and MSTP
Section II: Local and Telnet Management 212
Multiple
Spanning Tree
Instance (MSTI)
The individual spanning trees in MSTP are referred to as Multiple
Spanning Tree Instances (MSTIs). A MSTI can span any number of
AT-8400 Series switches, and an AT-8400 Series switch can support up to
16 MSTIs at a time.
To create a MSTI, you first assign it a number, referred to as the MSTI ID.
The range is 1 to 15. (The switch comes with a default MSTI with an MSTI
ID of 0. This default spanning tree instance is discussed later in Common
and Internal Spanning Tree (CIST) on page 220.)
Once you have selected an MSTI ID, you need to define the scope of the
MSTI by assigning one or more VLANs to it. An instance can contain any
number of VLANs, but a VLAN can belong to only one MSTI at a time.
Here are a couple of examples. Figure 75 illustrates two AT-8400 Series
switches each containing the two VLANs Sales and Production. The two
parts of each VLAN are connected with a direct link using untagged
ports on both switches.