Information about my New Blog Page (Nifty Financial Market)

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I will surely keep sharing critical and useful information through this blog as i get time.

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https://niftyfinancialmarket.blogspot.com

Fabric Extender Technology (FEX) in Nexus

Fabric Extender, the term marketed by Cisco, is basically a port extender as it is referenced in the developing IEEE 802.1Qbh (Bridge Port Extension). The 802.1Qbh standard is specific to control protocol used between the controlling bridge and the port extender, as it is referred in the draft. Supporting standards, also currently being developed like IEEE 802.1Qbg (Edge Virtual Bridging)  and IEEE 802.1Qbc

The Fabric Extender Architecture

The components involved:

Controlling Bridge (Parent Switch) to provide the control and management plane functions. This could be one or two Nexus 5000 or Nexus 7000 switches.
Port Extender which provides the physical port termination. This would be the Nexus 2000 series.
Connecting the FEX to the controlling bridge is done using SFPs over Ethernet fiber.
Encapsulation mechanism to transport frames from the FEX to the controlling bridge.
Control protocols to manage/monitor the FEXs

Cisco calls the encapsulation mechanism used on between the FEX and controlling bridge VN-Tag (previously VN-link). Controlling bridge is IEEE terminology, whereas parent switch is Cisco terminology. The IEEE 802.1Qbh working group was initiated by Cisco in a hope to standardize their VN-Tag technology. VN-Tag provides the capability to differentiate traffic between different host interfaces traversing the fabric uplinks. 

VN- Tag Header

The Fabric Extender Forwarding

A FEX or a Nexus 2000 operate as a remote linecard, but does not support local switching, all forwarding is performed on the parent switch. This is in contrast to most modular switches like the DFCs on Catalyst 6500. One of the reasons this was done was re-usability. By offloading the forwarding and intelligent decisions, the idea Cisco had in mind is that by upgrading the parent switch, the FEX being deployed in larger numbers can remain. Where the DFC on a Catalyst 6500 lives on the line card, the equivalent processing lives on the parent switch, be it the Nexus 7000/5000. Thus upgrading the parent switch upgrades that FEX capability since all it does is encapsulate traffic for identification. In large deployments where the cost of hundreds of FEXs out ways the cost of the Nexus 5000s used, this makes perfect sense. In very small deployments, this reason becomes arguable.

The Fabric Extender Management

It was briefly mentioned before that a parent switch and all its FEXs are treated as a single management device. This is accomplished by a small satellite image running on the FEX. This image is a smaller compatible version of the parent NX-OS image pushed from the parent switch. The parent switch is responsible for this and happens with no user involvement. Same applies to when the parent switch is upgraded, every attached FEX is upgraded during this time too.

The Fabric Extender Operation

Lets take a deep look at the backend operations. There are various interfaces involved:

1. HIF (Host Interface): Are the physical user/host interfaces on the FEX. These interfaces receive normal Ethernet traffic before it is encapsulated with the VN-Tag header. Each HIF interface is assigned a unique VN-Tag ID that is used with the encapsulation.

2. NIF (Network Interface): Physical uplink interfaces on the FEX. These interfaces can only connect back to the parent switch and carries only VN-Tagged traffic.

3. LIF (Logical Interface): Is the logical interface representation of the HIF and its configuration on the parent switch. Forwarding decisions are based on the LIF.

4. VIF (Virtual Interface): Is a logical interface on the FEX. The parent switch assigns/pushes the config of a LIF to the VIF of an associated FEX which is mapped to a physical HIF. This is why replacing a FEX becomes trivial in that the broken FEX is unplugged and the replacement is plugged in.

Nexus Switches Overview

Cisco Nexus Family of products has become extremely popular in small and large data centers thanks to their ability of unifying storage, data and networking services.
Also the Cisco Fabric Interconnect can provide a rock-solid programmable platform that fully supports any virtualized environment.

The Cisco Nexus family includes a generous number of different Nexus models to meet the demands of any Data Center environment.

Nexus Family Switch

Cisco Nexus Family consists of following series types

1) CISCO NEXUS 9000 SERIES SWITCHES
The Data Center switches of Nexus 9000 can operate in Cisco NX-OS Software or Application Centric Infrastructure (ACI) modes.
The main features of the new Cisco Nexus 9000 Series are: support of Fabric Extender Technology (FEX), virtual Port Channel (VPC) and Virtual Extensible LAN (VXLAN).

Nexus 9K Switches

2) CISCO NEXUS 7000 SERIES SWITCHES

The Data Center switches of 7K Nexus can provide an end-to-end data center architecture on a single platform, including data center core, aggregation, and access layer. The 7k series provides high-density 10, 40, and 100 Gigabit Ethernet interfaces. The main features of the Cisco Nexus 7000 Series are support for FEX, Virtual Port Channel (VPC), VDC, MPLS and Fabricpath. In addition, the N7K supports fairly robust and established technologies for multi-DC interconnect (DCI).

Nexus 7K Switches

3) CISCO NEXUS 5000 SERIES SWITCHES
The Data Center switches of 5K provides access layer (End of Row), providing architectural support for virtualization and Unified Fabric environments. Cisco Nexus 5000 Series can support VXLAN and comprehensive Layer 2 and 3 features for scaling data center networking. It supports Native Fibre Channel, Ethernet, and FCoE interfaces. The default system software includes most Cisco Nexus 5000 Platform features, such as Layer 2 security and management features. Licensed features include: Layer 3 routing, IP multicast and enhanced Layer 2 (Cisco Fabric Path).

Nexus 5K Switches

4) CISCO NEXUS 3000 SERIES SWITCHES
The product family offers features such as latency of less than a microsecond, line-rate at Layer 2 & 3 unicast, multicast switching, and the support of 40 Gigabit Ethernet interfaces. The Cisco Nexus 3000 Series switches are positioned for use in environments with ultra-low latency requirements such as financial High-Frequency Trading (HFT), High-Performance Computing (HPC) and automotive crash-test simulation Applications.

Nexus 3K Switches

The Cisco Nexus 3000 platform offers more than 15 models to satisfy all the switching needs an organization might have. The Nexus 3000 series offers switches starting with 1GE ports (Nexus 3000) and scales all the way up to 32 port 100GE ports with the Nexus 3232C model. Environments sensitive to delays will surely benefit from this series as they have been designed to practically eliminate any switching latency while at the same time offering large buffer spaces per port.