MSTP region for this check. The value of Max Hops (below) is used to limit hops within an
MSTP region.
The maximum age must satisfy the following constraints:
2 X (Hello Time + 1.0 seconds) < max message age < 2 X (forward delay – 1.0 seconds)
Hello Time (1 to 10; Default = 2): Configuration messages (BPDUs) are sent periodically to
other bridges based on a time period labeled hello time. Decreasing the hello time gives faster
recovery times; increasing the hello time interval decreases the overhead involved.
The hello time must satisfy the following constraints:
2 x (hello time + 1.0 seconds) < max message age < 2 x (forward delay - 1.0 seconds)
Forward Delay (4 to 30; Default = 15): The forward delay is a time (in seconds) used by all
switches in the network. This value is controlled by the root bridge and is used as a timeout
value to allow ports to begin forwarding traffic after network topology changes. If a port is
not configured as an edge port and RSTP cannot negotiate the link status, a port must wait
twice the forward delay before forwarding network traffic. In a properly configured network
using RSTP (not STP) this setting has very little effect. For STP networks, setting the time
too short may allow temporary loops when the network structure changes (switches turn on
or off or links are added or broken). A longer time will prevent temporary loops, but network
traffic will be disrupted for a longer time.
The default value for the forward delay is 15 seconds. If you change this setting, the switch
will not allow a value unless it satisfies the following formula:
2 × (hello time + 1.0 seconds) < max message age < 2 x (forward delay - 1.0 seconds)
Transmission Limit (1 to 10; Default = 6): The transmission limit controls the maximum
number of BPDUs that can be sent in one second.
The transmission limit can range from 1 to 10 messages/second (6 messages/second default).
Increasing Transmission limit can speed convergence of the network but at the cost of
configuration messages using a larger share of the available network bandwidth.
Region Name (MSTP): The region name is used together with the configuration revision
and VLAN to MSTI (MST Instance) mapping to define an MSTP region.
Configuration Revision (MSTP; 0 – 65535): The configuration revision is used together
with the region name and VLAN to MSTI (MST Instance) mapping to define an MSTP
region.
Max Hops (MSTP; 6 to 40; Default = 20): Max Hops determines the maximum number of
switches a BPDU will be propagated through within an MSTP region. This value is used to
prevent old data from endlessly circulating within a region.
MST Instances: For MSTP, you can configure multiple spanning tree instances. Add an
instance by clicking Add MSTI. For each MSTI, you can configure a name, the MST ID,
and this bridge’s priority in that spanning tree.
NOTE: Assign all Switches in an RSTP/STP network the same Max Age.
4-20
Chapter 4 - Managed Switch Software Setup
Stride Industrial Ethernet Switches User Manual 2nd Ed. Rev. A
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