Fabric Extender

Nexus 2000 Overview

• N2K Fabric Extender (FEX) acts as a remote linecard of 7K or 5K chassis• All management performed on Parent Switch– No console or VTY ports on FEX– NX-OS automatically downloaded from Parent• No local switching– Traffic between local ports on FEX must flow “north”via uplink to Parent and then “south” back down– Can impact design decision of platform placement

FEX Types

Top of Many Rack

End of Row Rack

Middle of Row Rack

Top of Row Rack

Advantages

FEX Terminology

• Fabric Interface• Host Interface• Logical Interface• Virtual Interface

Virtual Network Tag

Tag InfoThe VNTag is inserted between the source MAC address and the IEEE

802.1Q fields from the original Ethernet frame. The VNTag fields are :

• Ethertype: This field identifies a VNTag frame. IEEE reserved the value 0x8926 for Cisco VNTag.

• Direction bit (d): A 0 indicates that the frame is traveling from the FEX to the parent switch. A 1 means that the frame is traveling from the parent switch to the FEX.

• Pointer bit (p): A 1 indicates that a Vif_list_id is included in the tag. A 0 signals that a Dvif_id is included in the frame.

Tag Info• Virtual Interface List Identifier (Vif_list_id): This is a 14-bit value mapped to a listof

host interfaces to which this frame must be forwarded.

• Destination Virtual Interface Identifier (Dvif_id): This is a 12-bit value mapped toa single host interface to which an Ethernet frame will be forwarded.

• Looped bit (l): This field indicates a multicast frame that was forwarded out the switch port and later received. In this case, the FEX checks the Svif_id and filters the frame from the corresponding port.

• Reserved bit (r): This bit is reserved for future use.

• Source Virtual Interface Identifier (Svif_id): This is a 12-bit value mapped to the host interface that received this frame (if it is going from the FEX to the parent switch).

5K vs 7K

5K as FEX’s Parent– Supports Static Pinning & vPC Topologies– FEX ports are L2 switchports

• 7K as FEX’s Parent– Not all line cards support FEX– Static Pinning only

• FEX link must be Port-Channel– FEX ports are L2 switchports or native L3 routedinterfaces

SDP

7000 Basic requirement

Other Requirement

Connection Option

Static Pinning

Initialize FEX feature set– feature fex on N5K– install feature-set fex & feature-set fex on N7K• Configure downlinks to FEX– switchport mode fex– fex associate [num]– 7K requires Port-Channel to FEX• FEX should be discovered by Parent– show fex [detail]– NX-OS download to FEX takes a few minutes– Once complete FEX appears as just normal ports on Parent

Port channel

Design

Prepositioning

Question???