ZyXEL Communications XGS4600 Series User Manual page 177

Table 66 Advanced Application > Spanning Tree Protocol (continued)
LABEL DESCRIPTION
Forwarding Delay This is the time (in seconds) the root switch will wait before changing states (that is, listening to
(second) learning to forwarding).
Note: The listening state does not exist in RSTP.
Cost to Bridge This is the path cost from the root port on this Switch to the root switch.
Port ID This is the priority and number of the port on the Switch through which this Switch must
communicate with the root of the Spanning Tree.
Topology This is the number of times the spanning tree has been reconfigured.
Changed Times
Time Since Last This is the time since the spanning tree was last reconfigured.
Change
SLOT This field appears only in stacking mode. Click the drop-down list to choose the slot number of
the Switch in a stack.
Port This field displays the number of the port on the Switch. In stacking mode, the first number
represents the slot ID and the second is the port number.
Port State This field displays the port state in STP.
• Discarding – The port does not forward or process received frames or learn MAC
addresses, but still listens for BPDUs.
• Learning – The port learns MAC addresses and processes BPDUs, but does not forward
frames yet.
• Forwarding – The port is operating normally. It learns MAC addresses, processes BPDUs
and forwards received frames.
Port Role This field displays the role of the port in STP.
• Root – A forwarding port on a non-root bridge, which has the lowest path cost and is the
best port from the non-root bridge to the root bridge. A root bridge does not have a root
port.
• Designated – A forwarding port on the designated bridge for each connected LAN
segment. A designated bridge has the lowest path cost to the root bridge among the
bridges connected to the LAN segment. All the ports on a root bridge (root switch) are
designated ports.
• Alternate – A blocked port, which has a best alternate path to the root bridge. This path is
different from using the root port. The port moves to the forwarding state when the
designated port for the LAN segment fails.
• Backup – A blocked port, which has a backup or redundant path to a LAN segment
where a designated port is already connected when a switch has two links to the same
LAN segment.
• Disabled – Not strictly part of STP. The port can be disabled manually.
Designated Bridge This field displays the identifier of the designated bridge to which this port belongs when the
ID port is a designated port. Otherwise, it displays the identifier of the designated bridge for the
LAN segment to which this port is connected.
Designated Port ID This field displays the priority and number of the bridge port (on the designated bridge),
through which the designated bridge transmits the stored configuration messages.
Designated Cost This field displays the path cost to the LAN segment to which the port is connected when the
port is a designated port. Otherwise, it displays the path cost to the root bridge from the
designated port for the LAN segment to which this port is connected.
Root Guard State This field displays the state of the port on which root guard is enabled.
• Root – inconsistent – the Switch receives superior BPDUs on the port and blocks the port.
• Forwarding – the Switch unblocks and allows the port to forward frames again.
Chapter 13 Spanning Tree Protocol
XGS4600 Series User's Guide
177