Brocade Communications Systems 53-1002163-02 manual Configuring Rstp

7 RSTP overview

With RSTP, the port roles for the new interface states are also different. RSTP differentiates explicitly between the state of the port and the role it plays in the topology. RSTP uses the root port and designated port roles defined by STP, but splits the blocked port role into backup port and alternate port roles:

•Backup port—Provides a backup for the designated port and can only exist where two or more ports of the switch are connected to the same LAN; the LAN where the bridge serves as a designated switch.

•Alternate port—Serves as an alternate port for the root port providing a redundant path towards the root bridge.

Only the root port and the designated ports are part of the active topology; the alternate and backup ports do not participate in it.

When the network is stable, the root and the designated ports are in the forwarding state, while the the alternate and backup ports are in the discarding state. When there is a topology change, the new RSTP port roles allow a faster transition of an alternate port into the forwarding state.

For more information on RSTP, see “STP, RSTP, and MSTP configuration and management” on page 64.

Configuring RSTP

To configure RSTP, perform the following steps from global configuration mode.

1.Enable RSTP using the global protocol spanning-treecommand. For details, see “Enabling STP, RSTP, or MSTP” on page 64.

switch(config)#protocol spanning-tree rstp

2.Designate the root switch using the bridge-prioritycommand. For details, see “Specifying the bridge priority” on page 65. The range is 0 through 61440 and the priority values can be set only in increments of 4096.

switch(conf-rstp)#bridge-priority 28672

3.Configure the bridge forward delay value. For details, see “Specifying the bridge forward delay” on page 66.

switch(conf-rstp)#forward-delay 20

4.Configure the bridge maximum aging time value. For details, see “Specifying the bridge maximum aging time” on page 66.

switch(conf-rstp)#max-age 25

5.Enable the error disable timeout timer value. For details, see “Enabling the error disable timeout timer” on page 67.

switch(conf-rstp)#error-disable-timeout enable

6.Configure the error-disable-timeoutinterval value. For details, see “Specifying the error disable timeout interval” on page 67.

7.switch(conf-rstp)#error-disable-timeout interval 60

8.Configure the port-channel path cost method. For details, see “Specifying the port-channel path cost” on page 67.

switch(conf-rstp)#port-channel path-cost custom

9.Configure the bridge hello time value. For details, see “Specifying the bridge hello time (STP and RSTP)” on page 68.

60	Converged Enhanced Ethernet Administrator’s Guide
	53-1002163-02