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NX-OS is a network operating system designed by Cisco Systems for their own Nexus-series Ethernet switches and MDS-series Fibre Channel storage area network switches. NX-OS is designed to support high performance, high reliability server access switches used in the data center. NX-OS evolved from the Cisco MDS operating system, SAN-OS. SAN-OS was originally developed for the MDS line of switches.[1]

It is based on MontaVista Software embedded Linux. It is inter-operable with other Cisco operating systems. It runs on both the Nexus and MDS product lines by Cisco.

NX-OS command-line interface is IOS-like. However, some features need to be enabled explicitly first before configuring.[2]

One of the unique features of NX-OS is ITD (Intelligent Traffic Director).

ITD is a hardware based multi-Tbps Layer 4 load-balancing, traffic steering and clustering solution on Nexus 7000 series of switches. It supports IP-stickiness, resiliency, NAT (EFT), VIP, health monitoring, sophisticated failure handling policies, N+M redundancy, IPv4, IPv6, VRF, weighted load-balancing, bi-directional flow-coherency, and IPSLA probes including DNS. There is no service module or external appliance needed. ITD is available on Nexus 7000/7700 series in NX-OS 6.2(8) or later. It will also be available on Nexus 5k/6k. ITD is much superior than legacy solutions like PBR, WCCP, ECMP, port-channel, layer-4 load-balancer devices.


  • Features 1
  • Switches running NX-OS 2
  • Cisco NX-OS and Cisco IOS Comparison 3
  • Releases 4
  • See also 5
  • External links 6
  • References 7


Switches running NX-OS

  • Nexus B22 (HP, Dell, Fujitsu)
  • Nexus 7700 series
  • Nexus 7000 series
  • Nexus 6000 series
  • Nexus 5000 series
  • Nexus 4000 (for IBM BladeCenter)
  • Nexus 2000 series
  • Nexus 3000
  • Nexus 1000V
  • MDS 9700 FC Directors
  • MDS 9500 FC Directors[3]
  • MDS 9250i FC Switch
  • MDS 9222i FC Switch
  • MDS 9100 FC Switches

Cisco NX-OS and Cisco IOS Comparison

If you are familiar with traditional Cisco IOS command-line interface (CLI), the CLI for NX-OS is similar to Cisco IOS. There are key differences that should be understood prior to working with NX-OS, however:

■ When you first log into NX-OS, you go directly into EXEC mode.

■ NX-OS has a setup utility that enables a user to specify the system defaults, perform basic configuration, and apply a predefined Control Plane Policing (CoPP) security policy.

■ NX-OS uses a feature-based license model. An Enterprise or Advanced Services license is required depending on the features required.

■ A 120-day license grace period is supported for testing, but features are automatically removed from the configuration after the expiration date is reached.

■ NX-OS has the capability to enable and disable features such as OSPF, BGP, and so on via the feature configuration command. Configuration and verification commands are not available until you enable the specific feature.

■ Interfaces are labeled in the configuration as Ethernet. There aren’t any speed designations in the interface name. Interface speed is dynamically learned and reflected in the appropriate show commands and interface metrics.

■ NX-OS supports Virtual Device Contexts (VDC), which enable a physical device to be partitioned into logical devices. When you log in for the first time, you are in the default VDC.

■ The Cisco NX-OS has two preconfigured instances of VPN Routing Forwarding (VRF) by default (management, default). By default, all Layer 3 interfaces and routing protocols exist in the default VRF. The mgmt0 interface exists in the management VRF and is accessible from any VDC. If VDCs are configured, each VDC has a unique IP address for the mgmt0 interface.

■ Secure Shell version 2 (SSHv2) is enabled by default. (Telnet is disabled by default.)

■ Default login administrator user is predefined as admin; a password has to be specified when the system is first powered up. With NX-OS, you must enter a username and password; you cannot disable the username and password login. In contrast, in IOS you can simply type a password; you can optionally set the login to require the use of a username.

■ NX-OS uses a kickstart image and a system image. Both images are identified in the configuration file as the kickstart and system boot variables; this is the same as the Cisco Multilayer Director Switch (MDS) Fibre Channel switches running SAN-OS.

■ NX-OS removed the write memory command; use the copy running-config startup-config; there is also the alias command syntax.

■ The default Spanning Tree mode in NX-OS is Rapid-PVST+.

Caution : In NX-OS, you have to enable features such as OSPF, BGP, and CTS; if you remove a feature via the no feature command, all relevant commands related to that feature are removed from the running configuration.[4]


4.1, 4.2, 5.0, 5.1, 5.2, 6.0, 6.1, 6.2

See also

External links

  • intro
  • data sheet
  • ITD at-a-glance
  • ITD information
  • RISE at-a-glance
  • RISE information


  1. ^ Cisco NX-OS Software: Business-Critical Cross-Platform Data Center OS
  2. ^ Nexus: Hands on with NX-OS, Part#1
  3. ^ Cisco Product Brocuhure Cisco MDS 9500 Series of Multilayer Directors, visited 18 May 2012
  4. ^ NX-OS and Cisco Nexus Switching

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