Siemens S223, S323 user manual Designated Port and Root Port, Port Priority

User Manual	UMN:CLI
SURPASS hiD 6615 S223/S323 R1.5

i

Designated Port and Root Port

A Root Port is the port in the active topology that provides connectivity from the Desig- nated Switch toward the root. A Designated Port is a port in the active topology used to forward traffic away from the root onto the link for which this switch is the Designated Switch. That is; except root port in each switch, selected port to communicate is desig- nated port.

Port Priority

Meanwhile, when path-costs of two paths are same, port-priority is compared. As the be- low picture, suppose that two switches are connected. Since the path-costs of two paths are 100, same, their port priorities are compared and port with smaller port priority is se- lected to transmit packet.

All these functions are automatically performed by BPDU, which is the information of switch. It is also possible to configure BPDU to modify root switch or path manually.

-Path-cost 100

-Port priority 7

Root	- Port 1
	Path 1

Path 2

-Path-cost 100

-Port priority 8

-Port 2

( path-cost of PATH 1 = path-cost of PATH 2 = 100 ∴ unable to compare

PATH 1 port priority = 7, PATH 2 port priority = 8, PATH 1＜ PATH 2, ∴ PATH 1 is chosen )

Fig. 8.12 Port Priority

A50010-Y3-C150-2-7619 203