Supermicro SSE-G2252, User Manual

Page: 197 / 1401

Chapter 8: Spanning Tree Algorithm
Configuring Interface Settings for STA
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Range: 0-240, in steps of 16
•
Admin Path Cost – This parameter is used by the STA to determine
the best path between devices. Therefore, lower values should be
assigned to ports attached to faster media, and higher values assigned
to ports with slower media. Note that path cost takes precedence over
port priority. (Range: 0 for auto-configuration, 1-65535 for the short
path cost method, 1-200,000,000 for the long path cost method)
3
By default, the system automatically detects the speed and duplex
mode used on each port, and configures the path cost according to the
values shown below. Path cost “0” is used to indicate auto-configuration
mode. When the short path cost method is selected and the default
path cost recommended by the IEEE 8021w standard exceeds 65,535,
the default is set to 65,535.
•
Admin Link Type – The link type attached to this interface.
•
Point-to-Point – A connection to exactly one other bridge.
•
Shared – A connection to two or more bridges.
•
Auto – The switch automatically determines if the interface is
attached to a point-to-point link or to shared media. (This is the
default setting.)
•
Root Guard – STA allows a bridge with a lower bridge identifier (or
same identifier and lower MAC address) to take over as the root bridge
at any time. Root Guard can be used to ensure that the root bridge is
not formed at a suboptimal location. Root Guard should be enabled on
any designated port connected to low-speed bridges which could
potentially overload a slower link by taking over as the root port and
forming a new spanning tree topology. It could also be used to form a
3. Refer to
“Configuring Global Settings for STA” on page 193
for information on
setting the path cost method. The range displayed on the STA interface configuration
page shows the maximum value for path cost. However, note that the switch still
enforces the rules for path cost based on the specified path cost method (long or
short).
Table 8-1: Recommended STA Path Cost Range
Port Type IEEE 802.1D-1998 IEEE 802.1w-2001
Ethernet 50-600 200,000-20,000,000
Fast Ethernet 10-60 20,000-2,000,000
Gigabit Ethernet 3-10 2,000-200,000
Table 8-2: Default STA Path Costs
Port Type Short Path Cost
(IEEE 802.1D-1998)
Long Path Cost
(IEEE 802.1D-2004)
Ethernet 65,535 1,000,000
Fast Ethernet 65,535 100,000
Gigabit Ethernet 10,000 10,000