Brocade Converged Enhanced Ethernet Administrator's Guide v6.1.2_cee (53-1001258-01, June 2009)

48 Converged Enhanced Ethernet Administrator’s Guide
53-1001258-01
STP, RSTP, and MSTP configuration procedures
4
Specifying the bridge forward delay
In any mode (STP, RSTP, or MSTP), use this command to specify how long an interface remains in
the listening and learning states before the interface begins forwarding all spanning-tree
instances. STP interface states are as follows:
• Listening—The interface processes the Bridge Protocol Data Units (BPDUs) and waits for new
information that might cause it to return to the blocking state.
• Learning—The interface does not forward frames (packets), instead it learns source addresses
from frames received and adds them to the filtering database (switching database).
• Forwarding—The interface is receiving and sending data which is the normal operation. The
STP still monitors incoming BPDUs that can indicate the interface should return to the blocking
state to prevent a loop.
• Blocking—The interface might cause a switching loop, no user data is sent or received, but the
interface might go to the forwarding state if the other links in use fail and the STP determines
that the interface may transition to the forwarding state. BPDU data continues to be received
in the blocking state.
To specify the bridge forward delay, perform the following steps from Privileged EXEC mode:
Step Task Command
1. Enter global configuration mode. switch>#config t
Enter configuration commands, one
per line. End with CNTL/Z.
switch(config)#
2. Enter a mode (STP, RSTP, or MSTP). switch(config)#protocol
spanning-tree stp
3. Specify the bridge forward delay. The range is 4 through
30 seconds. The default is 15 seconds. The following
relationship should be kept:
2*(forward_delay - 1)>=max_age>=2*(hello_time + 1)
switch(conf-stp)#forward-delay
seconds
4. Display the spanning-tree configuration. switch(conf-stp)#do show
spanning-tree