Contemporary Control Systems Compact Managed Switches Software Manual for Console Access - Manual (Page 39)

TD020850-0MG
39
4.3.9.2.1 Version
The original 1990 link-management specification in IEEE802.1D, Clause 8, described
path redundancy via the Spanning Tree Protocol (STP). In 1999 STP was superseded
by the Rapid Spanning Tree Protocol (RSTP) of IEEE802.1D, Clause 17. The RSTP
interoperates with STP, but if RSTP-compliant switches are used in the same network
with legacy STP-compliant switches, rapid reconfiguration may not be possible. RSTP
is the default selection for managed switches from Contemporary Controls.
4.3.9.2.2 Hello Time
This is the interval at which the root device transmits a configuration message. The default
value is 2 seconds, and can be set from 1–10 seconds. But if the result of the equation
(Max Age / 2) – 1
is less than 10, the maximum Hello Time will be the calculated value.
4.3.9.2.3 Priority (of the entire switch)
You can adjust the switch priority in steps of 4096 (the default is 32768) as follows :
0, 4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768, 36864, 40960, 45056, 49152, 53248, 57344, 61440.
4.3.9.2.4 Max Age
This is the maximum number of seconds a device waits to receive a configuration frame
before attempting to reconfigure. The default value is 20 seconds, and it can be set from
6–40 seconds. However, actual minimum and maximum limits may be imposed by
calculations based on the Hello Time and Forward Time as follows :
If the result of the equation
2 x (Hello Time + 1)
is more than 6, the minimum Max Age will be the calculated value.
If the result of the equation
2 x (Forward Time – 1)
is less than 40, the maximum Max Age will be the calculated value.
4.3.9.2.5 Forward Delay
This is the time a device will wait before changing states. Each device must receive
topology information before it forwards frames and each port needs time to listen for any
information that might force it to a discarding state. The default value is 15 seconds, and
can be set from 4–30 seconds. But if the result of the equation
(Max Age / 2) + 1
is more than 4, the minimum Forward Delay will be the calculated value.
NOTE: The value limits for Hello Time, Max Age and Forward Delay will only be imposed if the
RSTP/STP field has been Enabled.