Allied Telesis AT-WA7500 - Manual (Page 119)

AT-WA7500 User’s Guide
119
7. On the root access point and the access point at the endpoint of the
IP tunnel, select Predefined Subtype Filters. If you have end devices
communicating using IP, set these filters to Pass:
‰ DIX ARP
‰ ICMP
8. 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.
Using One IP
Multicast
Address for
Multiple IP
Tunnels
IP tunneling supports IP multicast and Internet Group Management
Protocol (IGMP). IP multicast provides an ideal way to distribute IP hello
messages. These hello messages are only forwarded to those IP subnets
and IP hosts (such as access points) that participate in the multicast
group. IP multicast has these advantages:
‰ You do not have to know the unicast or directed broadcast IP
addresses in advance.
‰ IP multicast provides better built-in redundancy than IP unicast,
because any access point can establish an IP tunnel.
IGMP is a standard protocol that lets you originate multiple IP tunnels
using one IP multicast address. It allows IP multicast frames to be routed
to remote IP subnets that have hosts participating in the multicast
group. Note that IGMP is independent of IP; it can be used to facilitate
multicast for IP or any other application. IGMP has these advantages:
‰ Causes IP hello messages to be forwarded only to those subnets
that participate in the IP multicast group
‰ Increases redundancy because multiple access points on a remote
subnet can receive IP hello messages
IP routers only forward multicast frames to those subnets that have IP
hosts that participate in the respective IP multicast group. An IP host
uses IGMP to notify IP routers that it wants to participate in an IP
multicast group.
Access points can act as IP hosts and participate in an IP multicast group
by enabling IGMP. The Internet Assigned Numbers Authority has
allocated 224.0.1.65 for Inter Access Point protocol (IAPP). You must
enter this address in the IP address list in the root access point. (Note
that the address list may contain other IP addresses.) and in the Multicast
Address field in the other access points.