Allied-telesis AT-S63 Manual de usuario descargar pdf (Pagina 252)

100

101

Chapter 16: STP and RSTP

252 Section II: Advanced Features

Path Costs and Port Costs

After the root bridge has been selected, the bridges must determine if

the network contains redundant paths and, if one is found, they must

select a preferred path while placing the redundant paths in a backup or

blocking state.

Where there is only one path between a bridge and the root bridge, the

bridge is referred to as the designated bridge and the port through which

the bridge is communicating with the root bridge is referred to as the

root port.

If redundant paths exist, the bridges that are a part of the paths must

determine which path will be the primary, active path, and which path(s)

will be placed in the standby, blocking mode. This is accomplished by an

determination of path costs. The path offering the lowest cost to the root

bridge becomes the primary path and all other redundant paths are

placed into blocking state.

Path cost is determined through an evaluation of port costs. Every port

on a bridge participating in STP has a cost associated with it. The cost of

a port on a bridge is typically based on port speed. The faster the port,

the lower the port cost. The exception to this is the ports on the root

bridge, where all ports have a port cost of 0.

Path cost is simply the sum of the port costs between a bridge and the

root bridge.

The port cost of a port on an AT-9400 Series switch is adjustable through

the AT-S63 management software. For STP, the range is 0 to 65,535. For

RSTP, the range is 0 to 20,000,000.

Port cost also has an Auto-Detect feature. This feature allows spanning

tree to automatically set the port cost according to the speed of the port,

assigning a lower value for higher speeds. Auto-Detect is the default

setting. Table 15 lists the STP port costs with Auto-Detect.

Table 13. STP Auto-Detect Port Costs

Port Speed Port Cost

10 Mbps 100

100 Mbps 10

1000 Mbps 4

1 2 ... 247 248 249 250 251 252 253 254 255 256 257 ... 709 710

Comentarios a estos manuales

Sin comentarios

Allied-telesis AT-S63 Manual de usuario Pagina 252

Comentarios a estos manuales

Relacionado con productos y manuales para Hardware De La Computadora Allied-telesis AT-S63