Spanning Tree Protocol; Chapter 25 Spanning Tree Protocol; Rstp And Stp; Table 48 Path Cost - ZyXEL Communications IES-1248-51 User Manual

This chapter introduces the Spanning Tree Protocol (STP) and Rapid Spanning Tree Protocol
(RSTP).

25.1 RSTP and STP

RSTP adds rapid reconfiguration capability to STP. The IES-1248 supports RSTP and the
earlier STP. RSTP and STP detect and break network loops and provide backup links between
switches, bridges or routers. They allow a device to interact with other RSTP or STP-aware
devices in your network to ensure that only one path exists between any two stations on the
network. The Integrated Ethernet Switch uses RSTP by default but can still operate with STP
switches (although without RSTP's benefits).
The root bridge is the base of the spanning tree; it is the bridge with the lowest identifier value
(MAC address). Path cost is the cost of transmitting a frame onto a LAN through that port. It is
assigned according to the speed of the link to which a port is attached. The slower the media,
the higher the cost, as illustrated in the following table.

Table 48 Path Cost

Path Cost
Path Cost
Path Cost
Path Cost
Path Cost
Path Cost
On each bridge, the root port is the port through which this bridge communicates with the root.
It is the port on this Integrated Ethernet Switch with the lowest path cost to the root (the root
path cost). If there is no root port, then this Integrated Ethernet Switch has been accepted as
the root bridge of the spanning tree network.
For each LAN segment, a designated bridge is selected. This bridge has the lowest cost to the
root among the bridges connected to the LAN.

Chapter 25 Spanning Tree Protocol

Spanning Tree Protocol

RECOMMENDED
LINK SPEED
VALUE
4Mbps
10Mbps
16Mbps
100Mbps
1Gbps
10Gbps
IES-1248-51/51A/53 User's Guide
C
H A P T E R
RECOMMENDED
RANGE
250 100 to 1000
100 50 to 600
62 40 to 400
19 10 to 60
4 3 to 10
2 1 to 5
2 5
ALLOWED RANGE
1 to 65535
1 to 65535
1 to 65535
1 to 65535
1 to 65535
1 to 65535
187