Allied Telesis AT-WL2411 - Manual (Page 91)

AT-WL2411 Installation and User’s Guide
91
An IP tunnel is established when an access point on a remote IP subnet
attaches to the root access point through its IP tunnel port. The number
of IP tunnels the root access point can originate is practically unlimited.
However, the IP address list can presently contain eight entries. The size
of the address list effectively limits the number of tunnels that can be
created if unicast and directed broadcast IP addresses are used;
however, you can use a single IP multicast address to originate a
practically unlimited number of tunnels.
The IP address list can contain any combination of IP unicast, IP
broadcast, or IP multicast addresses. Only one IP tunnel can be created
for each IP unicast address in the list. A single IP multicast address can be
used to create a practically unlimited number of tunnels to multiple
remote IP subnets. A single IP directed broadcast address can be used to
create a practically unlimited number of tunnels to a single remote IP
subnet. (An IP directed broadcast address is typically used to specify all
hosts on a single remote subnet.)
A remote IP subnet functions much like a wireless secondary LAN with
these exceptions:
❑ Any access point can provide a wireless link to another access
point. Only the root access point can originate an IP tunnel.
❑ A wireless link can provide a transparent bridge for both wired
and wireless devices on a wireless secondary LAN. An IP tunnel
only provides a transparent bridge for end devices (unless
explicitly configured to provide connectivity for an NNL gateway
on a remote IP subnet).
Establishing
and
Maintaining IP
Tunnels
If the IP tunnel port control is enabled, the root access point sends hello
messages to each IP address in its IP address list. An access point on a
remote IP subnet automatically establishes an IP tunnel if it receives an
IP hello message from the root access point. An access point attached
through an IP tunnel transmits hello messages on the remote subnet so
that other access points on the remote subnet that do not receive IP
hello messages can also attach to the network.
If IP hello messages are sent to IP unicast addresses, then some access
points on a remote subnet will not receive hello messages; therefore,
those access points cannot establish an IP tunnel. If bridging is disabled
on the subnet, wireless traffic is forwarded to and from these access
points through data link tunnels. A data link tunnel is logically
concatenated with an IP tunnel so that wireless traffic can be completely
isolated from the remote IP subnet.
If you need to bridge to a remote subnet, see “Configuring the Spanning
Tree Parameters” earlier in this chapter.