CHAPTER 7
REPEATING FEATURES
Revised: 9 Sep 11
7-3
EST P/N AA107A
SPANNING TREE PROTOCOL
The ESTeem Model 195Ea uses standard Ethernet Rapid Spanning Tree Protocol (RSTP) to determine the radio routing structure
of the wireless network. The primary purpose of RSTP is to make sure that “network loops” are not created. A network loop is
having two communication paths to the same destination where the remote device would receive the same data multiple times. If
there were no way to control the data flow, this data would be constantly passed around this loop causing a “packet storm” that
would shut down the entire network. The Spanning Tree Protocol will block all these redundant links.
The STP operation begins by determining which Ethernet device on the network will be the Root Bridge. All Ethernet networks
have a Root Bridge that is selected by the lowest MAC address. All path costs are evaluated against this Root Bridge device to
determine routing and which paths will be blocked. On a wired Ethernet network, the location of the Root Bridge is not really
important, but in a wireless network selection of the Root Bridge is critical to the wireless network routing. Let’s use one of the
Example network diagrams from Chapter 5 to continue the discussion (Figure 4).
Access Point Router
with Repeater
Feature Enabled
10/100BaseT
HUB or Switch
Mobile
PLC
EtherStation
Mode
10/100BaseT
Access Point Bridge
with Repeater
Feature Enabled
Primary Re
peater Pa
th
Ba
ck
up
Re
pea
te
r Pa
th
Access Point Bridge
with Repeater
Feature Enabled
Mobile Vehicle
Single Ethernet Device
Example #4
S/N: 14004
Pr
ima
ry
Re
pea
te
r Pa
th
Plant Network
Large Wired LAN
Example #1
S/N: E-14001
WLAN MAC=00:04:3F:00:09:01
Remote Building
Small Ethernet Wired LAN
Example #3
S/N: E-14003
WLAN MAC=00:04:3F:00:09:10
Stand-Alone Repeater Site
Example #2
S/N: E-14002
WLAN MAC= 00:04:3F:00:09:05
Network
Router
(Required)
Figure 4: Programming Example #1 Diagram