Transition Networks
S4224 Web User Guide
33558 Rev. C
Page 464 of 669
Monitor > Spanning Tree > Port Status
The
Monitor
>
Spanning Tree
>
Port Status
menu path displays the STP Port Status table, which
provides the STP CIST port status for the S4224 physical ports.
An MSTn instance is local to a region. ISTs in different regions are interconnected via a Common
Spanning Tree (CST). The Common and Internal Spanning Tree (CIST) includes the collection of ISTs in
each MST region, and the CST that connects the ISTs.
As a result of the spanning-tree calculation, ports will assume various roles in the topology. A root port is
a port facing towards the root that is connected to the ‘best path’ back to the root.
‘Best path’ means:
1) the path with the lowest cost back to the root,
2) the path going through the device with the lowest BID if there is more than device advertising the
lowest cost, and
3) the lowest port ID on that device if there is more than one connection to the device.
The STP Port Status table parameters are explained below.
Port
The S4224 port number of the logical STP port.
CIST Role
The current STP port role of the CIST port. The port role value can be:
AlternatePor
t
: An alternative path to the root bridge. This path is different than using the root port.
BackupPort
: A backup/redundant path to a segment where another bridge port already connects.
RootPort
:
Port by which frames leave a device to reach the root (forwarding port). This refers to a
forwarding port that is the best port from Nonroot-bridge to Rootbridge.
DesignatedPort
: Port by which frames enter a device to reach the root (forwarding port).
A forwarding port for every LAN segment. A Non-Designated port is a Port blocking frames to prevent
a loop in the topology (blocking port).
Disabled
: Not strictly part of STP, a network administrator can manually disable a port.
Non-STP
: the port is not STP-capable.