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NX-OS CLI for IOS Administrators

January 11, 2014

IOS has been around for decades and has built up quite a bit of muscle memory in administrators’ fingers. But lets be honest, IOS isn’t perfect. Cisco revisited the NX-OS CLI to improve it but kept it similar to IOS so retraining should be mostly minimal.

Interface Names

Cisco’s IOS devices have always indicated the theoretical port speed in the interface command. For example, the first Ethernet port on a stackable Fast Ethernet switch would be designated FastEthernet 1/0/1. NX-OS refers to all Ethernet ports as…Ethernet. Ethernet1/0/1 would be the first Ethernet port in the first slot of a Nexus 7000 chassis. Personally, this is a welcome change as it abstracts out the speed. Because the speed command can change the speed anyways, implying port speed in the title can be incorrect. Furthermore, many Nexus ports can use either 1GbE or 10GbE transceivers so names other than Ethernet would be a misnomer.

Say Goodbye to the “Do” Command

show commands have always been present in operational mode in IOS and still are in NX-OS. However, the do command is no longer required to access commands present in operational mode. Nothing replaces it either, just type the command as you would in operational mode. Hallelujah!

Router02(config)# int eth2/1
Router02(config-if)# ip add 1.1.1.1 255.255.255.0
Router02(config-if)# no shut
Router02(config-if)# show int e2/1 brief
------------------------------------------------------------------------------
Ethernet        VLAN        Type    Mode        Status  Reason      Speed       Port
Interface                                               Ch #
------------------------------------------------------------------------------
Eth2/1          --        eth   routed      up      none        1000(D)     --
Router02(config-if)# 

All Hail CIDR Notation

Tired of typing subnet masks in IOS? NX-OS now supports CIDR notation.

Router02(config)# int eth2/1
Router02(config-if)# ip add 1.1.1.1/24

No More User EXEC Mode

NX-OS does away with User EXEC Mode. If you don’t recall what that means, it is the original command prompt you get when you log in which is suffixed by a >.

Router02> 

All User EXEC functions are now merged into Privileged EXEC mode. AKA…

Router02# 

No More Spanning Tree PortFast

PortFast is a Cisco proprietary term and the one IOS used. The Spanning Tree standard, 802.1D, uses the phrases “edge port” and “network port”. Enabling PortFast equivalent functionality isn’t hard on NX-OS, just a little different.

Router02(config-if)# spanning-tree port type edge

Alternatively, a switch-to-switch connection could be configured using:

Router02(config-if)# spanning-tree port type network

Modular Functionality

Boot up a brand new Nexus switch and configure an OSPF instance. Try it, I dare you. It won’t work. Features can be enabled or disabled using the feature command.

Router02(config)# feature ospf
LAN_ENTERPRISE_SERVICES_PKG license not installed. ospf feature will be shutdown after grace period of approximately 120 day(s)
Router02(config)#

Besides OSPF, other optionally enabled features which can be used are:

  • BGP
  • vPC
  • OTV
  • DHCP

There are others, but it gives an idea of some of the functionality which can be enabled or disabled.

Conclusion

Many other differences between IOS and NX-OS exist and I will point them out in other trainings. These are the high-level ones and I’m sure are a must on the CCNA DC exam.

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