learning curve IOS->NX-OS

[ashirel]

we may be migrating our 4500 chassis to a nexus/FEX arrangement.

i'm interested in hear from those who after years on IOS experience introduced NX-OS to thier environment.

similar enough command sets? or is it as if a different manufacturer was introduced ?

tnx,

ams

[Steve Fuller]

Hi,

The Cisco Nexus with NX-OS is obviously a different platform from Cisco Catalyst switches with IOS and will take some learning and getting used to. We've found differences between NX-OS and IOS, but not so many that engineers that are used to Cisco IOS aren't able to pick up and learn NX-OS.

Cisco NX-OS has been available for many years now and has matured and gained feature parity in many respects, but if you migrate, I think you'll still find features you've used on IOS for some time that are different or simply not supported in NX-OS.

A couple of places to start to look for differences are as follows:

• IOS-NXOS Configuration Conversion Tool
• Cisco Nexus 7000 NX-OS/IOS Comparison Tech Notes

For the Nexus 2000 series Fabric Extenders you would probably also want to understand some of the quirks around their connectivity to the upstream Nexus switch, and connectivity of devices to the host interfaces of the FEX. For example the host interfaces run Spanning Tree BPDU Guard, and this can't be disabled. That means you can't connect a switch to a host interface of the FEX unless you enable features like Spanning Tree BPDU filter.

If you want to understand some of those issues perhaps take a read of the Data Center Access Design with Cisco Nexus 5000 Series Switches and 2000 Series Fabric Extenders and Virtual PortChannels design guide. It's a long document though.

There's plenty of material out there, but if you're only considering migration at this stage it may not be worth the required time to read at this point in time.

I guess my summary would be that NX-OS is different, but not so much so that your engineers won't cope.

Regards

[ashirel]

thanks for the info steve.

u mention docs that refer to nexus 5k and 7k.

we're considering a 9372 switch. 

is the 9k line worse, same or better on this issue.

tnx,

ams

[Steve Fuller · Accepted solution]

Hi,

The Nexus 9000 running NX-OS (as opposed to ACI) is pretty much the same in terms of the command usage etc., and should be no different to learning NX-OS on that platform vs. learning it on the Nexus 5000 or 7000. I think you'll find that most of what's shown on the Nexus 7000 NX-OS/IOS Comparison Tech Notes will be applicable to the N9K also.

There are certain features such as FabricPath that supported on the N5K and N7K that are not going to be supported on the N9K, but this would only be an issue if trying to integrate the N9K into an existing N5K/N7K environment. As you're not going to be doing that it's not a problem you'll encounter.

Regards

[ashirel]

ah, that last  point is especially interesting because if we introduce 1 nexus, chances

r we'll be introducing more.

i know that w/ cisco, a higher # product line doesn't mean much w/ reference to

when the line was introduced nor how advanced it is.  in this particular case i understand

that the 9k line is both newer and more advanced than the 5k/7k line.

true?

if so, then chances r that i wouldn't be deploying any of the later.

btw, do u agree that if the # of ports needed (including future expansion x pi) doesn't

exceed what i get from a nexus switch (not chassis) + 2 FEX's, there's almost no justification to going w/ a chassis. we're going w/ 2 sets of nexus/FEX's for redundancy.

tnx,

ams

[Steve Fuller]

Hi,

in this particular case i understand that the 9k line is both newer and more advanced than the 5k/7k line. true?

It's certainly newer, but whether it's more "advanced" is a matter for debate. I'd say that at this stage the Nexus 7000, having been around for six or seven years, has many capabilities that the Nexus 9000 doesn't and the implementations are more mature with considerable field exposure.

The Nexus 9000 with NX-OS has other capabilities such as VXLAN that are not supported on the older Nexus 7000 series modules, but the newer modules have support and OS support is not far behind. The Nexus 9000 also has ACI capability if you ever want to go down that particular path.

For data centre LAN the Nexus 9000 is probably more cost effective than the N7K, but Cisco are still pushing Nexus 7000 for functions such as OTV, Border Router functionality for Nexus 9000 VXLAN fabrics etc.

At the end of the day you need to understand the requirements and choose the most appropriate platform at the cost that's right for you.

do u agree that if the # of ports needed (including future expansion x pi) doesn't exceed what i get from a nexus switch (not chassis) + 2 FEX's, there's almost no justification to going w/ a chassis

In certain environments I think there's less need for chassis based switches today, but again it's understanding the environment or what you see in the mist of the crystal ball. The Nexus 9300 at the access/edge will today support 16 FEX and 768 server interfaces so you can go pretty large with a pair of switches.

If you then consider connecting these in some kind of Clos based spine-leaf topology with the spine scaled out to four or six switches, then you can build a fabric that's large enough to meet most requirements while still allowing you to sleep at night. Whatever the technology, there's always going to be something that's a "single point of failure" so don't go putting all your eggs in one basket.

The obvious advantage of chassis based switches is that if in the future you want to move from 10GE to 40GE and then to 100GE, you don't have to swap the entire switch.

As with many things in this life, it depends.

Regards