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

42 Converged Enhanced Ethernet Administrator’s Guide
53-1001258-01
RSTP overview
4
Table 8 lists the interface state changes between STP and RSTP.
With RSTP, the port roles for the new interface states have also changed. RSTP differentiates
explicitly between the state of the port and the role it plays in the topology. It has adapted the STP
root port and designated port roles but has split 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.
To configure RSTP on your Brocade 8000 CEE switch, see “STP, RSTP, and MSTP configuration
procedures” on page 45.
TABLE 8 STP versus RSTP state comparison
STP interface state RSTP interface state Is the interface included in the
active topology?
Is the interface learning MAC
addresses?
Disabled Discarding No No
Blocking Discarding No No
Listening Discarding Yes No
Learning Learning Yes Yes
Forwarding Forwarding Yes Yes