LevelOne GTL-2881, User Manual

Page: 213 / 706

Chapter 7
| Spanning Tree Algorithm
Displaying Interface Settings for STA
– 213 –
◆
Oper Path Cost – The contribution of this port to the path cost of paths
towards the spanning tree root which include this port.
◆
Oper Link Type – The operational point-to-point status of the LAN segment
attached to this interface. This parameter is determined by manual
configuration or by auto-detection, as described for Admin Link Type in STA
Port Configuration on
page 207 .
◆
Oper Edge Port – This parameter is initialized to the setting for Admin Edge
Port in STA Port Configuration on page 207 (i.e., true or false), but will be set to
false if a BPDU is received, indicating that another bridge is attached to this
port.
◆
Port Role – Roles are assigned according to whether the port is part of the
active topology, that is the best port connecting a non-root bridge to the root
bridge (i.e.,
root port), connecting a LAN through the bridge to the root bridge
(i.e., designated port), is the MSTI regional root (i.e., master port), or is an
alternate or backup port that may provide connectivity if other bridges,
bridge ports, or LANs fail or are removed. The role is set to disabled (i.e.,
disabled port) if a port has no role within the spanning tree.
Figure 120: STA Port Roles
The criteria used for determining the port role is based on root bridge ID, root
path cost, designated bridge, designated port, port priority, and port number,
in that order and as applicable to the role under question.
Alternate port receives more
useful BPDUs from another
bridge and is therefore not
selected as the designated
port.
x
R: Root Port
A: Alternate Port
D: Designated Port
B: Backup Port
R R
A D B
Backup port receives more
useful BPDUs from the same
bridge and is therefore not
selected as the designated
port.
x
R R
A D B