Cisco NX-OS/IOS Configuration Fundamentals Comparison

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This tech note outlines the main differences for the configuration fundamentals between the Cisco NX-OS software and the Cisco IOS® Software. Sample configurations are included for Cisco NX-OS and Cisco IOS Software to illustrate some the differences after the first system startup. Please refer to the NX-OS documentation on for a complete list of supported features.

Cisco NX-OS Overview

The Cisco NX-OS is a data center class operating system designed for maximum scalability and application availability. The CLI interface for the NX-OS is very similar to Cisco IOS, so if you understand the Cisco IOS you can easily adapt to the Cisco NX-OS. However, a few key differences should be understood prior to working with the Cisco NX-OS.

Important Cisco NX-OS and Cisco IOS Software Differences

In Cisco NX-OS:

  • When you first log into the NX-OS, you go directly into EXEC mode.
  • Role Based Access Control (RBAC) determines a users permissions. There are no privilege leves or an enable secret.
  • By default, the admin user has network-admin rights that allow full read/write access.
  • The Cisco NX-OS has a Setup Utility that allows a user to specify the system defaults, perform basic configuration, and apply a pre-defined Control Plane Policing (CoPP) security policy.
  • The Cisco NX-OS uses a feature based license model. An Enterprise or Advanced Services license is required depending on the features required. Additional licenses may be required in the future.
  • A 120 day license grace period is supported for testing, but features are automatically removed from the configuration after the expiration date is reached.
  • The Cisco NX-OS has the ability to enable and disable features such as OSPF, BGP, etc… 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.
  • The Cisco NX-OS supports Virtual Device Contexts (VDCs), which allow 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 VRF instances by default (management, default).
  • SSHv2 is enabled by default. TELNET is disabled by default.
  • VTY and Auxiliary port configurations do not show up in the default configuration unless a parameter is modified (The Console port is included in the default configuration). The VTY port supports 32 simultaneous sessions and the timeout is disabled by default.

Things You Should Know

The following list provides some additional Cisco NX-OS information that should be helpful when configuring and maintaining the Cisco NX-OS.

  • The default administer user is predefined as admin. A password has to be specified when the system is powered up for the first time.
  • If you remove a feature via the no feature command, all relevant commands related to that feature are removed from the running configuration.
  • The 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.
  • The show running-config command accepts several options, such as OSPF, BGP, etc… that will display the runtime configuration for a specific feature.
  • The show tech command accepts several options that will display information for a specific feature.

Configuration Comparison

The following sample code show similarities and differences between the Cisco NX-OS software and the Cisco IOS Software CLI.

Default User Prompt
c6500> n7000#
Entering Configuration Mode
c6500# configure terminal n7000# configure terminal
Saving the Running Config to the Startup Config (nvram)
c6500# write memory


c6500# copy running-config startup-config

n7000# copy running-config startup-config
Erasing the startup config (nvram)
c6500# write erase n7000# write erase
Installing a License
Cisco IOS Software does not require a license file installation. n7000# install license bootflash:license_file.lic
Interface Naming Convention
interface Ethernet 1/1

interface FastEthernet 1/1

interface GigabitEthernet 1/1

interface TenGigabitEthernet 1/1

interface Ethernet 1/1
Default VRF Configuration (management)
Cisco IOS Software doesn’t enable VRFs by default. vrf context management
Configuring the Software Image Boot Variables
boot system flash sup-bootdisk:s72033-ipservicesk9_wan-mz.122-33.SXH1.bin boot kickstart bootflash:/n7000-s1-kickstart.4.0.4.bin sup-1

boot system bootflash:/n7000-s1-dk9.4.0.4.bin sup-1

boot kickstart bootflash:/n7000-s1-kickstart.4.0.4.bin sup-2

boot system bootflash:/n7000-s1-dk9.4.0.4.bin sup-2

Enabling Features
Cisco IOS Software does not have the functionality to enable or disable features. feature ospf
Enabling TELNET (SSHv2 is recommended)
Cisco IOS Software enables TELNET by default. feature telnet
Configuring the VTY Timeout and Session Limit
line vty 0 9

exec-timeout 15 0


line vty

session-limit 10

exec-timeout 15

Verification Command Comparison

The following table compares some useful show commands for verifying the initial system startup and running configuration.

Cisco NX-OS Cisco IOS Software Command Description
show running-config show running-config Displays the running configuration
show startup-config show startup-config Displays the startup configuration
- - -
show interface show interface Displays the status for all of the interfaces
show interface ethernet <x/x> show interface <int type> Displays the status for a specific interface
- - -
show boot show boot Displays the current boot variables
- - -
show clockshow clock Displays the system clock and time zone configuration
show clock detail show clock detail Displays the summer-time configuration
- - -
show environment show environment Displays all environment parameters
show environment clock show environment status clock Displays clock status for A/B and active clock
show environment fan show environment cooling fan-tray Displays fan status
show environment power show power Displays power budget
show environment temperature show environment temperature Displays environment data
- - -
show log logfile show log Displays the local log
show log nvram - Displays persistent log messages (severity 0-2) stored in NVRAM
show module show module Displays installed modules and their status
show module uptime - Displays how long each module has be powered up
show module fabric - Displays fabric modules and their current status
show platform fabric-utilization show fabric utilization Displays the % of fabric utilized per module
show process cpu show process cpu Displays the processes running on the CPU
show process cpu history show process cpu history Displays the process history of the CPU in chart form
show process cpu sorted show process cpu sorted Displays sorted processes running on the CPU
- - -
show system cores - Displays the core dump files if present
show system exception-info show exception Displays last exception log
show system redundancy status show redundancy Displays the supervisors High Availability status
show system resources show process cpu Displays CPU and memory usage data
show system uptime - Displays system and kernel start time (Displays active supervisor uptime)
- - -
show tech-support show tech-support Displays system technical information for Cisco TAC
show tech-support <name> show tech-support <name> Displays feature specific technical information for Cisco TAC
- - -
show version show version Displays running software version, basic hardware, CMP status and system uptime
- - -
show line show line Displays console and auxiliary port information
show line com1 - Displays auxiliary port information
show line console show line console 0 Displays console port information
show line console connected - States if the console port is physically connected
show terminal show terminal Displays terminal settings
show users show users Displays current virtual terminal settings
- - -
show vrf show ip vrf Displays a list of all configured VRFs
show vrf <name> show ip vrf <name> Displays an specified VRF
show vrf <name> detail show vrf detail <name> Displays details for a specified
show vrf <name> interface - Displays interface assignment for a specified VRF
show vrf default - Displays a summary of the default VRF
show vrf detail show vrf detail Displays details for all VRF's
show vrf interface show ip vrf interface Displays VRF interface assignment
show vrf management - Displays a summary of the management VRF
- - -
show license - Displays all license file information
show license brief - Displays the license file names installed
show license file <name> - Displays license contents based on a specified name
show license host-id - Displays the chassis Host-ID used for creating a license
show license usage - Displays all licenses used by the system
show license usage <license-type> - Displays all licenses used by the system per type
show license usage vdc-all - Displays all licenses used by the system for all VDCs
- - -
show vdc - Displays a list of the configured VDC's
show vdc <name> - Displays a summary of the individual VDC
show vdc <name> detail - Displays configuration details for a specific VDC
show vdc <name> membership - Displays interface membership for a specific VDC
show vdc <name> resource - Displays resource allocation for a specific VDC
show vdc current-vdc - Displays the VDC that the user is currently in
show vdc detail - Displays details information for all VDCs
show vdc membership - Displays interface membership for all VDCs
show vdc resources - Displays resource allocation for all VDCs

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