Spanning Tree - STP
General
Microsemi PDS-408G Web Management User Guide Ver. 1.0.1, 03-2019
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8
SPANNING TREE - STP
8.1
General
Spanning Tree Protocol (STP), and its variations as RSTP and MSTP, is used mainly for the following
reasons:
1. To prevent possible network loops, which without STP will cause broadcast storming.
2. Offer redundancy path from Switch to Switch or path to path over multiple Switches by supporting
network loops under the control of STP. The STP algorithm will make sure that at any given time
only one path out of multiple possible loops will be active, those allowing the Switch to use multiple
backup paths in case main connection path go down.
8.2
Spanning tree – Configuration - STP Config
Figure 8-1: STP Configuration
8.2.1
Basic Settings
Protocol Version
-The MSTP/RSTP/STP protocol version setting. Valid values are STP, RSTP, and
MSTP.
Bridge Priority
- Controls the bridge priority. Lower numeric values have better priority. The bridge
priority plus the MSTI instance number, concatenated with the 6-byte MAC address of the switch forms
a Bridge Identifier. For MSTP operation, this is the priority of the CIST. Otherwise, this is the priority of
the STP/RSTP bridge.
Forward Delay
- The delay used by STP Bridges to transit Root and Designated Ports to Forwarding
(used in STP compatible mode). Valid values are in the range 4 to 30 seconds.
Max Age
- The maximum age of the information transmitted by the Bridge when it is the Root Bridge.
Valid values are in the range 6 to 40 seconds, and MaxAge must be <= (FwdDelay-1)*2.
Maximum Hop Count
- This defines the initial value of remaining Hops for MSTI information generated
at the boundary of an MSTI region. It defines how many bridges a root bridge can distribute its BPDU
information to. Valid values are in the range 6 to 40 hops.
Transmit Hold Count
- The number of BPDUs a bridge port can send per second. When exceeded,
transmission of the next BPDU will be delayed. Valid values are in the range 1 to 10 BPDUs per
second.