Introduction; Chapter 10 Spanning Tree Protocol; Table 10-1 Recommended Path Cost - ZyXEL Communications Dimension ES-2008 User Manual

10.1 Introduction

Spanning Tree Protocol) is a standardized method (IEEE 802.1D) that eliminates loops in
a network by disabling some ports and allowing other ports to forward traffic based on the
parameters you configured. STP ensures that there is only one path between a specific
source and destination so packets will not travel in loops.
STP provides path redundancy while preventing undesirable loops in the network. STP
detects and breaks network loops and provides backup links between switches, bridges or
routers. It allows a device to interact with other STP-aware devices in your network to
ensure that only one path exists between any two stations on the network.
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. Refer to the following table for the recommended
path cost (in the allowed range between 1 and 65535) for each link speed.
LINK SPEED
4Mbps
10Mbps
16Mbps
100Mbps
1Gbps
10Gbps
On each bridge, the root port is the port through which a bridge communicates with the
root. It is the port on this switch with the lowest path cost to the root (the root path cost).
If there is no root port, then this switch has been accepted as the root bridge of the
spanning tree network.
Spanning Tree Protocol
Spanning Tree Protocol
This chapter describes the basics and configuration of STP.

Table 10-1 Recommended Path Cost

RECOMMENDED VALUE
250
100
62
19
4
2
Dimension ES-2008 Ethernet Switch
Chapter 10
RECOMMENDED RANGE
100 to 1000
50 to 600
40 to 400
10 to 60
3 to 10
1 to 5
10-1