Allied Telesis AT-S60 - Manual (Page 511)

Chapter 33: STP, RSTP, and MSTP
Section IV: Web Browser Management 510
All bridges in a single-instance bridged LAN use this aging time to
test the age of stored configuration messages called bridge
protocol data units (BPDUs). For example, if you use the default of
20, all bridges delete current configuration messages after 20
seconds. The range of this parameter is from 6 to 40 seconds. The
default is 20 seconds.
In selecting a value for maximum age, the following must be
observed:
MaxAge must be less then (2 x (HelloTime + 1))
MaxAge must be less then (2 x (ForwardingDelay - 1))
Bridge Max Hops
MSTP regions use this parameter to discard BPDUs. The Max Hop
counter in a BPDU is decremented every time the BPDU crosses an
MSTP region boundary. Once the counter reaches zero, the BPDU
is deleted.
Revision Level
The revision level of an MSTP region. This is an arbitrary number
that you assign to a region. The revision level must be the same on
all bridges in a region. Different regions can have the same
revision level without conflict. The range is 0 (zero) to 255.
6. Click Apply.
To save your changes, return to the General tab and click Save
Changes. The changes you made are saved on the switch. Or,
proceed to the next procedure to configure the CIST priority.
Configuring the
CIST Priority
To configure the CIST priority, perform the following procedure:
1. Display the Spanning Tree Expanded page for MSTP by performing
Steps 1 through 4 in the procedure Configuring MSTP Parameters
on page 507.
2. In the Configure CIST Parameters section, set the CIST Priority, the
priority number for the bridge.
This number is used to determine the root bridge of the bridged
network. This number is analogous to the RSTP bridge priority
value. The bridge in the network with the lowest priority number
is selected as the root bridge. If two or more bridges have the
same bridge or CIST priority values, the bridge with the
numerically lowest MAC address becomes the root bridge.
3. Click Apply.
To save your changes, return to the General tab and click Save
Changes. The changes you made are saved on the switch.