Configuration Commands
136
When configuring STP bridge parameters, the following formulas must be used:
• 2*(fwd-1) ≥ mxage
• 2*(hello+1) ≤ mxage
Spanning Tree port configuration
The default configuration for STP/PVST+ is off for downlink ports (1-16) and the management port (17),
and on for uplink ports (18-21). The default configuration for RSTP/MSTP is Spanning Tree off for all
downlink ports (1-16) and the management port (17), and on for all uplink ports (18-21), with downlink
ports configured as edge ports.
Spanning tree port parameters are used to modify STP operation on an individual port basis. STP port
parameters include:
• Port priority
• Port path cost
The following table describes the Spanning Tree Port Configuration commands.
Table 110 Spanning Tree Port Configuration commands
Command Description
spanning-tree stp {<1-128>}
priority {<0-255>}
Configures the port priority. The port priority helps determine which
bridge port becomes the designated port.
In a network topology that has multiple bridge ports connected to a
single segment, the port with the lowest port priority becomes the
designated port for the segment.
The range is 0 to 255, and the default is 128.
RSTP/MSTP: The range is 0 to 240, in steps of 16 (0, 16, 32...) and the
default is 128.
Command mode: Interface port
spanning-tree stp {<1-128>}
path-cost {<1-65535>}
Configures the port path cost. The port path cost is used to help
determine the designated port for a segment. Generally speaking, the
faster the port, the lower the path cost.
The range is 1 to 65535. The default is 100 for 10Mb ports, 10 for 100
Mb ports, 4 for Gigabit ports, and 2 for 10Gb ports.
A value of 0 indicates that the default cost will be computed for an auto-
negotiated link speed.
RSTP/MSTP: The range is 1 – 200000000, and the default it 20000 for
Gigabit ports, 2000 for 10Gb ports.
Command mode: Interface port
spanning-tree stp {<1-128>}
link {auto|p2p|shared}
Defines the type of link connected to the port, as follows:
• auto—Configures the port to detect the link type, and automatically
match its settings.
• p2p—Configures the port for Point-To-Point protocol.
• shared—Configures the port to connect to a shared medium (usually
a hub).
This command only applies when RSTP is turned on. See the “Common
Internal Spanning Tree configuration” section for more information.
Command mode: Interface port
