Multicast frames also trigger learning on edge switches, since several LAN protocols rely on source MAC address learning from multicast frames for proper forwarding.
VLAN designations and operation
VLANs can also be configured in Classic Ethernet and FabricPath mode, and conversational learning occurs automatically in VLANs configured for FabricPath mode. When a frame is carried across a FabricPath core port, the frame includes an IEEE 802.1Q tag with the original VLAN ID of the frame. So FabricPath core ports behave like 802.1Q trunks, and the VLAN ID is still used in the FabricPath core to control forwarding and flooding behavior, similar to Classic Ethernet networks, according to Cisco.
Edge ports that bridge FabricPath and Ethernet domains are always FabricPath interfaces belonging to FabricPath VLANs. Cisco FabricPath switches will have the same VLAN IDs as the Classic Ethernet switch connected to it, but with the VLAN mode configured as FabricPath -- VLANs configured for Classic Ethernet mode cannot be carried over a FabricPath core port.
As easy as Spanning Tree?
Although IS-IS forms the basis of FabricPath, users need not be IS-IS experts, Cisco notes. Users can enable FabricPath interfaces and begin forwarding FabricPath encapsulated frames in much the same way they can activate Spanning Tree and interconnect switches, Cisco ensures.
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