Beginning with Cisco NX-OS Release 5.1 and when you use an F Series
module, you can use conversational MAC address learning. You configure the type
of MAC address learning—conversational or traditional—by VLAN.
Conversational MAC address learning means that each interface learns
only those MAC addresses for interested hosts, rather than all MAC addresses in
the domain. Each interface learns only those MAC addresses that are actively
speaking with the interface. In this way, conversational MAC learning consists
of a three-way handshake.
This selective learning, or conversational MAC address learning, allows
you to scale the network beyond the limits of individual switch MAC address
All FabricPath VLANs use conversational MAC address learning.
CE VLANs use traditional MAC address learning by default, but you can
configure the CE VLANs to use conversational MAC learning.
Beginning with Cisco NX-OS Release 6.1, support for a Fabric Extender
(FEX) with VPC+ on F2 cards is available. To support forwarding with this
approach, core port learning is used.
The core port learning mode is enabled by default on F2 VDCs.