Allied Telesis AT-S62 - Manual (Page 485)

AT-S62 Menus Interface User’s Guide
Section IV: Spanning Tree Protocols 485
The second group can be applied independently on a port for each MSTI
where the port is a member. One of the parameters is the internal path
cost. This parameter specifies the port’s operating cost if it is connected
to a bridge that is a part of the same MSTP region. You can give a port a
different internal path cost for each MSTI where it is a member. This
group also has a parameter for setting port priority, used as a tie breaker
when two or more ports have equal costs to a regional root bridge.
Again, as with the internal path cost, you can assign a port a different
priority value for each of its MSTIs.
Multiple
Spanning Tree
Regions
Another important concept of MSTP is regions. A MSTP region is defined
as a group of bridges that share exactly the same MSTI characteristics.
Those characteristics are:
❑ Configuration name
❑ Revision level
❑ VLANs
❑ VLAN to MSTI ID associations
A configuration name is a name you assign to a region to help you
identify it. You must assign each bridge in a region exactly the same
name, even the same upper and lowercase lettering. Identifying the
regions in your network is easier if you choose names that are
characteristic of the functions of the nodes and bridges of the region.
Examples are Sales Region and Engineering Region.
The revision level is an arbitrary number you can assign to a region. You
can use the number to keep track of the revision level of a region’s
configuration. For example, you might use this value to maintain the
number of times you revise a particular MSTP region. It is not important
that you maintain this number, only that each bridge in a region have
the same number.
The bridges of a particular region must also have the same VLANs. The
names of the VLANs and the VIDs must be same on all bridges of a
region.
Finally, the VLANs in the bridges must be associated to the same MSTIs.
If any of the above information is different on two bridges, MSTP
considers the bridges as residing in different regions.