Cisco Nexus 2000 Series Fabric Extender

Cisco Nexus 2000 Series Fabric Extender

The Fabric Extender integrates with its parent switch, which is a Cisco Nexus Series device, to allow automatic provisioning and configuration taken from the settings on the parent device.

The Fabric Extender and its parent switch enable a large multipath, loop-free data centre topology without the use of the Spanning Tree Protocol (STP).

The Cisco Nexus 2000 Series Fabric Extender forwards all traffic to its parent Cisco Nexus Series device over 10-Gigabit Ethernet fabric uplinks, which allows all traffic to be inspected by policies established on the Cisco Nexus Series device.

No software is included with the Fabric Extender. The software is automatically downloaded and upgraded from its parent device.

Do not connect a bridge or switch to a host interface. These interfaces are designed to provide end host or server connectivity.

Host Interfaces

All Fabric Extender host interfaces run as spanning tree edge ports with BPDU Guard enabled and you cannot configure them as spanning tree network ports.

Any device that is running spanning tree connected to a Fabric Extender host interface results in that host interface being placed in an error-disabled state when a BPDU is received.

Fabric Extenders support the host vPC feature where a server can be dual-attached to two different FEXs through a port channel. You must configure parent switches that connect each Fabric Extender (one parent switch per FEX) in a vPC domain.

Minimum Number of Links on a Fabric Port Channel

In a network configuration of dual-homed hosts (active/standby), you can configure the Fabric Extender to support a minimum number of links for fabric port channels (FPCs) with the port-channel min-links command.

When the number of FPC links falls below the specified threshold, the host-facing Cisco Nexus 2000 interfaces are brought down. This process allows for a NIC switchover on the connection between the host and the FEX.

The automatic recovery of Cisco Nexus 2000 Series interfaces to the standby FEX is triggered when the number of FPC links reaches the specified threshold

Load Balancing Using Host Interface Port Channels

You can configure the load-balancing mode to apply to all Fabric Extenders or to specified ones. If load-balancing mode is not configured, Fabric Extenders use the default system configuration. The per-FEX configuration takes precedence over the load-balancing configuration for the entire system. You cannot configure the load-balancing method per port channel.

Switched Port Analyzer

You can configure the host interfaces on the Fabric Extender as Switched Port Analyzer (SPAN) source ports. You cannot configure Fabric Extender ports as a SPAN destination. Up to four SPAN sessions for host interfaces are supported on the same or different Fabric Extenders. Ingress source (Rx) monitoring is supported.

Management Model

The Cisco Nexus 2000 Series Fabric Extender is managed by its parent switch over the fabric interfaces through a zero-touch configuration model. The switch discovers the Fabric Extender by detecting the fabric interfaces of the Fabric Extender.

After discovery, if the Fabric Extender has been correctly associated with the parent switch, the following operations are performed:

1.  The switch checks the software image compatibility and upgrades the Fabric Extender if necessary.
2.  The switch and Fabric Extender establish in-band IP connectivity with each other.
3.  The switch pushes the configuration data to the Fabric Extender. The Fabric Extender does not store any configuration locally.
4.  The Fabric Extender updates the switch with its operational status. All Fabric Extender information is displayed using the switch commands for monitoring and troubleshooting.

Sample Commands:-

switch# configure terminal

switch(config)# feature-set fex

switch(config)# interface port-channel 4

switch(config-if)# switchport mode fex-fabric

switch(config-if)# fex associate 101

switch# show interface port-channel 4 fex-intf

Command or Action	Purpose
show environment fex {all | FEX-number} [temperature | power |fan]	Displays the environmental sensor status.
show inventory fex FEX-number	Displays inventory information for a Fabric Extender.
show module fex FEX-number	Displays module information about a Fabric Extender.
show sprom fex FEX-number {all | backplane | powersupply ps-num} | all	Displays the contents of the serial PROM (SPROM) on the Fabric Extender.