Allied Telesis AT-S63 - Manual (Page 268)

Chapter 16: STP and RSTP
268 Section II: Advanced Features
3. Adjust the following parameters as necessary.
1 - Force Version
This selection determines whether the bridge operates with RSTP
or in an STP-compatible mode. If you select RSTP, the bridge
operates all ports in RSTP, except for those ports that receive STP
BPDU packets. If you select Force STP Compatible, the bridge
operates in RSTP, using the RSTP parameter settings, but it sends
only STP BPDU packets out the ports.
2 - Bridge Priority
The priority number for the bridge. This number is used in
determining the root bridge for RSTP. The bridge with the lowest
priority number is selected as the root bridge. If two or more
bridges have the same priority value, the bridge with the
numerically lowest MAC address becomes the root bridge. When
a root bridge goes off-line, the bridge with the next priority
number automatically takes over as the root bridge. This
parameter can be from 0 (zero) to 61,440 in increments of 4096,
with 0 being the highest priority. For a list of the increments, refer
to Table 12, ”Bridge Priority Value Increments” on page 251.
3 - Bridge Hello Time
The time interval between generating and sending configuration
messages by the bridge. This parameter can be from 1 to 10
seconds. The default is 2 seconds.
4 - Bridge Forwarding
The waiting period before a bridge changes to a new state, for
example, becomes the new root bridge after the topology
changes. If the bridge transitions too soon, not all links may have
yet adapted to the change, possibly resulting in a network loop.
The range is 4 to 30 seconds. The default is 15 seconds. This
setting applies only to ports running in the STP-compatible mode.
5 - Bridge Max Age
The length of time after which stored bridge protocol data units
(BPDUs) are deleted by the bridge. All bridges in a 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 20, all bridges delete current configuration
messages after 20 seconds. This parameter can be from 6 to 40
seconds. The default is 20 seconds.
When you select a value for maximum age, observe the following
rules:
MaxAge must be greater than (2 x (HelloTime + 1)).
MaxAge must be less than (2 x (ForwardingDelay - 1))