How Stp Works; Stp Port States; Wep Encryption; Configuring The Wireless Screen - ZyXEL Communications ZyAIR G-5100 User Manual

ZyAIR G-5100 User's Guide

5.3.3 How STP Works

After a bridge determines the lowest cost-spanning tree with STP, it enables the root port and
the ports that are the designated ports for connected LANs, and disables all other ports that
participate in STP. Network packets are therefore only forwarded between enabled ports,
eliminating any possible network loops.
STP-aware bridges exchange Bridge Protocol Data Units (BPDUs) periodically. When the
bridged LAN topology changes, a new spanning tree is constructed.
Once a stable network topology has been established, all bridges listen for Hello BPDUs
(Bridge Protocol Data Units) transmitted from the root bridge. If a bridge does not get a Hello
BPDU after a predefined interval (Max Age), the bridge assumes that the link to the root
bridge is down. This bridge then initiates negotiations with other bridges to reconfigure the
network to re-establish a valid network topology.

5.3.4 STP Port States

STP assigns five port states (see next table) to eliminate packet looping. A bridge port is not
allowed to go directly from blocking state to forwarding state so as to eliminate transient
loops.

Table 12 STP Port States

PORT STATES
Disabled
Blocking
Listening
Learning
Forwarding

5.4 WEP Encryption

WEP encryption scrambles the data transmitted between the wireless stations and the access
points to keep network communications private. It encrypts unicast and multicast
communications in a network. Both the wireless stations and the access points must use the
same WEP key.

5.5 Configuring the Wireless Screen

Click the WIRELESS link under ADVANCED to display the Wireless screen. The screen
varies depending upon the operating mode you select.
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DESCRIPTIONS
STP is disabled (default).
Only configuration and management BPDUs are received and processed.
All BPDUs are received and processed.
All BPDUs are received and processed. Information frames are submitted to the
learning process but not forwarded.
All BPDUs are received and processed. All information frames are received and
forwarded.
Chapter 5 Wireless LAN