Spanning Tree

The switch is delivered with Spanning Tree default values set to those recommended by the IEEE 802.1D standard. These values are conservative worst-case estimates for LANs consisting of a large number of switches. Because of your network configuration, changing these default values may improve network performance.

Priority
Valid input: 0 to 65,535
Default value: 32768
Function: The device with the lowest priority value in a Spanning Tree becomes the root device (the starting point of the tree).

Message Age Timer Expiry
Valid input: 6 to 40 seconds
Default value: 20
Function: Defines the maximum time that information obtained from a Configuration BPDU can be used by the switch before it is discarded.
Comment: The 802.1D standard recommends setting the value such that: 2 x (Forward Delay Timer Expiry - 1.0 second) >= Message Age Timer Expiry and Message Age Timer Expiry >= 2 x (Hello Timer Expiry + 1.0 second)

Hello Timer Expiry
Valid input: 1 to 10 seconds
Default value: 2
Function: Specifies the time between transmissions of Configuration BPDUs when the switch is, or attempting to become, the root.
Comment: If the Hello Time expires (elapses), the switch generates a Configuration BPDU and forwards it to each LAN for which the switch is the Designated Switch. This relays knowledge of the Designated Root, Root Path Cost, Designated Switch, Designated Port and the values of various protocol timers.

Forward Delay Timer Expiry
Valid input: 4 to 30 seconds
Default value: 15
Function: Specifies the time a port is Listening and Learning while changing from Blocking to Forwarding.
Comment: When the Forward Delay Timer expires, the state changes from the Listening State (while moving from Blocking State to Learning State) to the Learning State (while moving from the Listening State to the Forwarding State).


More info about
Spanning Tree

How to
Change Spanning Tree values for the switch
Enable Spanning Tree on all ports


Procedures

*Legal Information © 2000 Intel Corporation