3com 5500-SI Manual De Usuario

C

HAPTER

 13: MSTP C

ONFIGURATION

Figure 42 illustrates primary MSTP terms (assuming that each switch in it has MSTP 
employed).

Figure 42   Basic MSTP terminologies

A multiple spanning tree (MST) region comprises multiple switches and the connected 
network segments. The switches are all MSTP-enabled and physically connected. They 
have the same region name, the same VLAN-to-spanning tree mapping 
configuration, and the same MSTP revision level configuration.

A switched network can contain multiple MST regions. You can group multiple 
switches into one MST region by using the corresponding MSTP configuration 
commands. For example, as shown in Figure 42, all switches in region A0 have the 
same MST region configuration: the same region name, the same VLAN-to-spanning 
tree mapping (that is, VLAN 1 is mapped to spanning tree instance 1, VLAN 2 is 
mapped to spanning tree 2, and the other VLANs are mapped to CIST), the same 
MSTP revision level (not shown in Figure 42).

A multiple spanning tree instance (MSTI) refers to a spanning tree in a MST region.

In a MST region, multiple spanning trees can be established independent of each 
other. For example, each region in Figure 42 can contain multiple spanning trees, 
known as MSTIs. Each of these spanning trees corresponds to a VLAN.

VLAN mapping table is a MST region attribute for describing how VLANs are mapped 
to MSTIs. For example, the VLAN mapping table of region A0 in Figure 42says: VLAN 
1 is mapped to MSTI 1; VLAN 2 is mapped to MSTI 2; and the other VLANs are 
mapped to CIST. In an MST region, load balancing is achieved according to the VLAN 
mapping table.