Chapter 5: Configuring the Spanning Tree
away from their root IP subnet.
Unicast frames are not flooded. Unicast frames are only forwarded outbound through an IP tunnel if the destination address identifies an end device that has roamed to a remote IP subnet. End devices attach to the root access point, which maintains entries for these devices in its forwarding database. The database entries indicate the correct subnet for outbound forwarding.
For TCP/IP applications, IP and ARP frames must be forwarded through IP tunnels. An IP or ARP frame is only forwarded outbound if the destination address identifies an end device on the root IP subnet. Usually, ARP requests (which are multicast frames) that originate on the root IP subnet are forwarded outbound to all devices on the network, including through IP tunnels to remote IP subnets. However, if you enable ARP flooding, ARP frames are only sent through the IP tunnel to the destination end device.
MAC frames that are forwarded outbound are encapsulated in the root access point, forwarded through the network, unencapsulated by the access point at the remote end of the IP tunnel, and forwarded to the appropriate access point (if necessary) for delivery to the destination end device.
Inbound Frames
Frames are forwarded inbound (to the primary LAN) through an IP tunnel if:
an end device is known to be attached to an access point on a remote IP subnet.
the frame type is configured to pass.
IP and ARP frames are only forwarded inbound through the IP tunnel if the source IP address belongs to the root IP subnet. Usually, these frames originate from wireless end devices that have roamed away from their root IP subnet. Frames transmitted by servers or wired devices that are connected to a remote IP subnet are not forwarded inbound through IP tunnels if the IP address does not belong to the root IP subnet.
MAC frames that are forwarded inbound are encapsulated by the access point at the remote end of the IP tunnel, forwarded through the IP tunnel to the root access point, unencapsulated, and placed on the network.
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