Sta Operation Levels; On The Bridge Level; On The Port Level; User-Changeable Sta Parameters - D-Link DES-3225G Series User Manual

24-port NWay Ethernet Switch User's Guide
♦ Automatic topology re-configuration When the path for which there is a backup path fails, the
backup path will be automatically activated, and STA will automatically re-configure the network
topology.

STA Operation Levels

STA operates on two levels: the bridge level and the port level. On the bridge level, STA calculates the Bridge
Identifier for each Switch, then sets the Root Bridge and the Designated Bridges. On the port level, STA sets
the Root Port and Designated Ports. Details are as follows:

On the Bridge Level

♦ Root Bridge The switch with the lowest Bridge Identifier is the Root Bridge. Naturally, you will want
the Root Bridge to be the best switch among the switches in the loop to ensure the highest network
performance and reliability.
♦ Bridge Identifier This is the combination of the Bridge Priority (a parameter that you can set) and
the MAC address of the switch. Example: 4 00 80 C8 00 01 00, where 4 is the Bridge Priority. A lower
Bridge Identifier results in a higher priority for the switch, and thus increases it probably of being
selected as the Root Bridge.
♦ Designated Bridge From each LAN segment, the attached Bridge that has the lowest Root Path Cost
to the Root Bridge is the Designated Bridge. It forwards data packets for that LAN segment. In cases
where all Switches have the same Root Path Cost, the switch with the lowest Bridge Identifier becomes
the Designated Bridge.
♦ Root Path Cost The Root Path Cost of a switch is the sum of the Path Cost of the Root Port and the
Root Path Costs of all the switches that the packet goes through. The Root Path Cost of the Root Bridge
is zero.
♦ Bridge Priority This is a parameter that users can set. The smaller the number you set, the higher
the Bridge Priority is. The higher the Bridge Priority, the better the chance the Switch will be selected
as the Root Bridge.

On the Port Level

♦ Root Port Each switch has a Root Port. This is the port that has the lowest Path Cost to the Root
Bridge. In case there are several such ports, then the one with the lowest Port Identifier is the Root
Port.
♦ Designated Port This is the port on each Designated Bridge that is attached to the LAN segment for
which the switch is the Designated Bridge.
♦ Port Priority The smaller this number, the higher the Port Priority is. With higher Port Priority, the
higher the probability that the port will be selected as the Root Port.
♦ Path Cost This is a changeable parameter and may be modified according to the STA specification.
The 100Mbps segment has an assigned Path Cost of 10, and each 10Mbps segment has an assigned Path
Cost of 100, based on the STA specifications.

User-Changeable STA Parameters

The factory default setting should cover the majority of installations. However, it is advisable to keep the
default settings as set at the factory; unless, it is absolutely necessary. The user changeable parameters in the
Switch are as follows:
Switch Management Concepts 27