nx.os.and.cisco.nexus.switching.2nd.edition.1587143046

encapsulated in a FabricPath header. From these interface types, three roles are defined for
switches carrying traffic across the fabric.
First, the ingress FabricPath switch receives a frame on one of its connected edge ports. The
ingress FabricPath switch is responsible for performing a MAC table lookup to determine
which SID has advertised reachability for the destination MAC address. The ingress
FabricPath switch also determines to which interface the frame should be forwarded. The
ingress FabricPath switch forwards the frame accordingly. Next, a core FabricPath switch
receives frames on a FabricPath core port and determines the next-hop interface based on
the SID in the FabricPath header. The core FabricPath switch forwards the frame
accordingly. Finally, the egress FabricPath switch receives frames on a FabricPath core
port and examines the FabricPath header. Upon seeing that it is the destination SID, it uses
the Local Identifier (LID) field to determine which FabricPath edge port the frame needs to
be forwarded on. The egress FabricPath switch removes the FabricPath header and
forwards the frame to the appropriate CE port. The ingress and egress FabricPath switches
are also sometimes referred to as Layer 2 gateways.
Through the use of these defined functions, MAC address learning can be optimized through
conversational learning. In traditional Ethernet implementations each switch unconditionally
populates its MAC address table based on the source address of the frame. This causes the
switch to consume valuable resources, even if it is just a transit switch. In the case of
FabricPath, traditional learning is done only on FabricPath edge ports. FabricPath core
switches do not need to learn any MAC addresses. At the FabricPath edge, only local MAC
addresses are unconditionally learned. The edge switch learns only the source MAC
address if the destination MAC is already present in its local MAC table.
Enabling FabricPath on a Nexus 7000 has the following prerequisites:
• You must install the Enhanced Layer 2 license.
• You must be using F1, F2, or F2e linecards for all FabricPath interfaces.
The first step in FabricPath configuration is to enable the corresponding feature-set, as
shown in Example 2-73.
Example 2-73. Enabling the FabricPath feature-set
Click here to view code image
fp-spine-1(config)# install feature-set fabricpath
fp-spine-1(config)# feature-set fabricpath
When the prerequisites are met, and the FabricPath feature set is enabled, you can begin the
configuration tasks associated with FabricPath. For the remainder of this chapter, the
topology shown in Figure 2-9 will be used.