Spanning Tree Protocol (Stp); Rapid Stp; Stp Terminology - ZyXEL Communications NWA-3160 - V3.70 Manual

Chapter 8 Wireless Screen

8.3.1 Spanning Tree Protocol (STP)

Spanning Tree Protocol (STP) detects and breaks network loops and provides
backup links between switches, bridges or routers. It allows a bridge to interact
with other STP-compliant bridges in your network to ensure that only one route
exists between any two stations on the network.

8.3.1.1 Rapid STP

The NWA uses IEEE 802.1w RSTP (Rapid Spanning Tree Protocol) that allow faster
convergence of the spanning tree (while also being backwards compatible with
STP-only aware bridges). Using RSTP topology change information does not have
to propagate to the root bridge and unwanted learned addresses are flushed from
the filtering database. In RSTP, the port states are Discarding, Learning, and
Forwarding.

8.3.1.2 STP Terminology

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 - see the following table.
Table 27 STP Path Costs
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 switch with the lowest path cost to the root (the
root path cost). If there is no root port, then this bridge 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.
144
RECOMMENDE
LINK SPEED
D VALUE
4Mbps 250
10Mbps 100
16Mbps 62
100Mbps 19
1Gbps 4
10Gbps 2
RECOMMENDE ALLOWED
D RANGE RANGE
100 to 1000 1 to 65535
50 to 600 1 to 65535
40 to 400 1 to 65535
10 to 60 1 to 65535
3 to 10 1 to 65535
1 to 5 1 to 65535
NWA-3160 Series User's Guide