Alcatel-Lucent 6850-48 Reference Guide

Distributed Spanning Tree Commands

OmniSwitch CLI Reference Guide

page 15-43

Configures the bridge forward delay time value for the flat mode Common and Internal Spanning Tree 
(CIST) instance. This value is the amount of time, in seconds, that determines how fast a port changes its 
Spanning Tree state until it reaches a forwarding state. The forward delay time specifies how long a port 
stays in the listening and learning states, which precede the forwarding state.

bridge cist forward delay seconds

Forward delay time in seconds (4–30).

By default, the bridge forward delay time value is set to 15 seconds.

OmniSwitch 6400, 6850, 6855, 9000, 9000E

• A low forward delay time can cause temporary loops in the network, because data may get forwarded 

before the reconfiguration message has reached all nodes on the network.

• The forward delay time is also used to age out all dynamic MAC address entries in the forwarding 

table (MAC address table) when a topology change occurs. 

• This command is an explicit Spanning Tree command that only applies to the flat mode CIST instance 

regardless of which operating mode (flat or 1x1) or protocol is active on the switch.

• If the switch is running in 1x1 mode when this command is used, the specified forward delay time 

value is not active for the CIST instance until the operating mode for the switch is changed to the flat 
mode.

• Note that when a configuration snapshot is taken of the switch, all Spanning Tree commands are saved 

in their explicit format. 

-> bridge mode flat

-> bridge cist forward delay 10

-> bridge cist forward delay 30

-> bridge mode 1x1

-> bridge cist forward delay 25

-> bridge cist forward delay 4

Release 6.1; command was introduced.