Allied Telesis AT-WA7500 - Manual (Page 109)

AT-WA7500 User’s Guide
109
About the
Primary LAN
and the Root
Access Point
The primary LAN (also called the root IP subnet) contains the root access
point, which initiates the spanning tree. When choosing the primary
LAN, ideally you should choose the IP subnet that contains gateways or
servers for the wireless end devices. However, these gateways and
servers may also be on another subnet.
The root coordinates the network and distributes common system
parameters to other access points and end devices. The root is elected
from a group of access points that are designated as root candidates
(access points that are powered on, active, and do not have a root
priority of 0). The root should not be an access point that handles a large
volume of wireless traffic. The access point with the highest root priority
is the root.
The election process also occurs in the event of a root access point
failure. Besides the root, you should have two or three access points with
a non-zero root priority. If two access points have the same root priority,
the access point with the highest Ethernet address becomes the root.
You should configure your network with overlapping coverage so that
the network can automatically recover from any single point of failure.
After the root access point is elected, it transmits hello messages on all
enabled ports. The spanning tree forms as other access points receive
hello messages and attach to the network on the optimal path to the
root. A non-root access point also transmits hello messages after it is
attached to the network. Each hello message contains the LAN ID of the
access point that originated the message. IAPP does not allow wireless
links to exist between access points that do not have matching LAN IDs.
To configure a root access point
1. On an access point that is installed on the primary LAN, from the Main
Menu select Spanning Tree Settings. The Spanning Tree Settings
screen appears.
2. Configure the LAN ID. All access points that want to participate in the
spanning tree must have the same LAN ID.
3. Set the Root Priority parameter to be the highest number of all access
points on the primary LAN. Verify that the Enable Ethernet Bridging
box is checked.
4. Verify that the Secondary LAN Bridge Priority is zero and the
Secondary LAN Flooding parameter is Disabled.
5. Select Submit Changes to save your changes. To activate your
changes, select Save/Discard Changes from the menu bar then Save
Changes and Reboot. For help, see Saving Configuration Changes
on page 41.