Overview This chapter provides an architectural overview of the Cisco Nexus 2000 Series Fabric Extender and includes the following sections: • Information About the Cisco Nexus 2000 Series Fabric Extender, page 2 • Fabric Extender Terminology, page 2 • Fabric Interface Features , page 3 •...
Information About the Cisco Nexus 2000 Series Fabric Extender The Cisco Nexus 2000 Series Fabric Extender, also known as FEX, is a highly scalable and flexible server networking solution that works with Cisco Nexus Series devices to provide high-density, low-cost connectivity for server aggregation.
In Cisco NX-OS Release 5.1 and earlier releases, the default port mode is Layer 2. To run a host interface in Layer 2 mode, use the switchport command. For Cisco NX-OS Release 5.2 and later releases, to change the port mode to Layer 3, use the no switchport command.
• You can connect any edge switch that leverages a link redundancy mechanism not dependent on spanning tree such as Cisco FlexLink or vPC (with the BPDU Filter enabled) to a Fabric Extender host interface. Because spanning tree is not used to eliminate loops, you should ensure a loop-free topology below the Fabric Extender host interfaces.
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.
Note Protocol Offload To reduce the load on the control plane of the Cisco Nexus Series device, Cisco NX-OS allows you to offload link-level protocol processing to the Fabric Extender CPU. The following protocols are supported: • Link Layer Discovery Protocol (LLDP) •...
• 1.2 to 1 oversubscription (48 host interfaces for four fabric interfaces) • 4.8 to 1 oversubscription (48 host interfaces for one fabric interface) Cisco Nexus 2000 Series NX-OS Fabric Extender Software Configuration Guide for Cisco Nexus 7000 Series Switches, Release 5.2...
Overview Management Model The Cisco Nexus 2248TP can be run with no oversubscription when its host interfaces are running in 100-Mb mode. The Cisco Nexus 2248TP-E Fabric Extender has 4 10-Gigabit Ethernet fabric interfaces and 48 100/1000BASE-T (100-Mb/1-Gigabit) Ethernet host interfaces. When its host interfaces are running in Gigabit Ethernet mode, it offers 1.2 to 1 oversubscription (48 host interfaces for four fabric interfaces).
Forwarding Model Forwarding Model The Cisco Nexus 2000 Series Fabric Extender does not perform any local switching. All traffic is sent to the parent switch that provides central forwarding and policy enforcement, including host-to-host communications between two systems that are connected to the same Fabric Extender as shown in the following figure.
• chassis is configured by the administrator. A Fabric Extender must be directly connected to its parent Cisco Nexus Series device via a port channel fabric interface. You configure a chassis ID on a port channel on the switch to identify the Fabric Extender that is discovered through those interfaces.
• port identifies the port number on a specific slot and chassis ID. Fabric Extender Image Management No software ships with the Cisco Nexus 2000 Series Fabric Extender. The Fabric Extender image is bundled into the system image of the parent switch. The image is automatically verified and updated (if required) during the association process between the parent switch and the Fabric Extender.
• All the uplinks and host ports of a Fabric Extender belong to a single VDC. The ports cannot be allocated or split among multiple VDCs. • You must connect the Fabric Extender to its parent Cisco Nexus 7000 Series device with a 32-port 10-Gigabit M1 module (N7K-M132XP-12), a 32-port, 10-Gigabit M1-XL module (N7K-M132XP-12L), an M2-Series module, or an F2-Series module.
The egress queuing parameters of the active network-QoS policy do not affect the FEX host-port queuing. Cisco Nexus 2000 Series NX-OS Fabric Extender Software Configuration Guide for Cisco Nexus 7000 Series Switches, Release 5.2...
FEX host interfaces includes the number of queues used, the mapping for each queue, the corresponding queue MTU, the enforced hardware queue limit, and the ingress and egress queue statistics. Cisco Nexus 2000 Series NX-OS Fabric Extender Software Configuration Guide for Cisco Nexus 7000 Series Switches, Release 5.2...
Port Statistics: rx drop rx mcast drop rx error tx drop mux ovflow ---------------+---------------+---------------+---------------+-------------- InActive Priority-flow-control enabled: no Cisco Nexus 2000 Series NX-OS Fabric Extender Software Configuration Guide for Cisco Nexus 7000 Series Switches, Release 5.2...
Interface is not in this module. • ISSU Behavior In Cisco NX-OS Release 6.2(2) and later releases, FEX queuing is disabled by default on all existing FEXs after an in-service software upgrade (ISSU). FEX queuing is enabled upon flapping the FEX. You can reload the FEX to enable queuing on any FEX after an ISSU.
The queue limit is enabled by default for all FEXs, regardless of whether queuing is enabled or disabled for the FEX. In Cisco NX-OS Release 6.2(2), all FEXs come up with the default hardware queue-limit value. Any user-defined queue limit that is configured after an ISSU by using the hardware queue-limit command takes effect even if queuing is not enabled for the FEX.
The MTU that is configured on a FEX port must match the MTU in the network-QoS policy map so that the FEX MTU can be applied to the FEX host interfaces. For more information, see the Cisco Nexus 7000 Series NX-OS Quality of Service Configuration Guide.