Brocade FastIron Ethernet Switch Platform and Layer 2 Switching Configuration Guide - Manual (Page 276)

Point-to-point ports
To take advantage of the 802.1W features, ports on an 802.1W topology should be explicitly
configured as point-to-point links using the CLI. Shared media should not be configured as point-to-
point links.
NOTE
Configuring shared media or non-point-to-point links as point-to-point links could lead to Layer 2 loops.
The topology in the following figure is an example of shared media that should not be configured as
point-to-point links. In this figure, a port on a bridge communicates or is connected to at least two
ports.
FIGURE 42 Example of shared media
Bridge port states
Ports roles can have one of the following states:
• Forwarding - 802.1W is allowing the port to send and receive all packets.
• Discarding - 802.1W has blocked data traffic on this port to prevent a loop. The device or VLAN can
reach the root bridge using another port, whose state is forwarding. When a port is in this state, the
port does not transmit or receive data frames, but the port does continue to receive RST BPDUs.
This state corresponds to the listening and blocking states of 802.1D.
• Learning - 802.1W is allowing MAC entries to be added to the filtering database but does not permit
forwarding of data frames. The device can learn the MAC addresses of frames that the port
receives during this state and make corresponding entries in the MAC table.
• Disabled - The port is not participating in 802.1W. This can occur when the port is disconnected or
802.1W is administratively disabled on the port.
A port on a non-root bridge with the role of Root port is always in a forwarding state. If another port on
that bridge assumes the Root port role, then the old Root port moves into a discarding state as it
assumes another port role.
A port on a non-root bridge with a Designated role starts in the discarding state. When that port
becomes elected to the Root port role, 802.1W quickly places it into a forwarding state. However, if the
Designated port is an Edge port, then the port starts and stays in a forwarding state and it cannot be
elected as a Root port.
A port with an Alternate or Backup role is always in a discarding state. If the port role changes to
Designated, then the port changes into a forwarding state.
Point-to-point ports
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