EtherChannel behavior in NX-OS

February 9th, 2010

I’ve had a lot of discussions with clients about the behavior of Port-Channel interfaces and their associated physical counterparts.  It’s necessary for many parameters of the physical and logical interfaces to be the same.  Here’s the behavior within NX-OS and the preferred way that I make changes to EtherChannels.

In this, we’re going to continue working with the logical interface Po100 and the physical interfaces Eth1/19 and Eth1/20 which will be in the EtherChannel. Read the rest of this entry »

Why EtherChannels should be used for FEX interfaces

February 8th, 2010

I prefer to use port-channel interfaces for the fabric interfaces when connecting fabric extenders (FEXs). If a single interface in the bundle fails, it won’t remove the fabric extender interface – it simply reduces it’s bandwidth. This results in stable, predictable, redundant and resilient behavior. Let’s prove this point. Read the rest of this entry »

Cisco WAAS – weird error when trying to register WAEs to the central manager

February 5th, 2010

When working on a WAE 500 (I know, this is really old hardware), I ran into an issue when trying to register with the central manager (CM):

waas-edge#sh cms info
Device registration information :
Device Id                            = 216
Device registered as                 = WAAS Application Engine
Current WAAS Central Manager         =
Registered with WAAS Central Manager =
Status                               = Pending(CM is busy, retry later)
Time of last config-sync             = Fri Feb  5 09:20:12 2010            

CMS services information :
Service cms_ce is running

Here’s how I resolved it! Read the rest of this entry »

Experimenting with Static Pinning

February 4th, 2010

What happens when more links are associated with an FEX than are permitted in the max-links parameter? Let’s find out…

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The FEX information is cached until it’s re-assigned to a different FEX

February 2nd, 2010

Continuing our journey into the world of FEXs on the Nexus 5000 and 2000, today we’re going to look at the behavior of the FEX configs themselves on the Nexus 5000.

All of the configuration and software information (firmware/images) for the FEX (Nexus 2148T) are kept on the parent switch (a Nexus 5000-series switch). Going on this, what happens when the FEX goes offline? Do I lose my config?

A stack of 3750 switches can be provisioned ahead of time, so that as stack members are added (assuming that they’re the correct type/model), no changes must be made – just move on. What kind of behavior is available on the Nexus 5000/2000?

I haven’t found provisioning available yet for FEXs on the N5k, however I did notice that the configurations for the FEX are retained when the FEX goes offline and online. This is great — if the 2148T fails or the fabric interface links are disconnected, the config will still be there (although not visible until the FEX comes back online). This article is looking at it from an association perspective (N2148T association with the N5k, not a configuration (actual port configs on the FEX). With that said, let’s explore this further… Read the rest of this entry »

What happens when the wrong serial number is entered for the FEX?

January 31st, 2010

Continuing on the journey of FEXs on the Nexus platform, we’re exploring about serial numbers being statically bound to an FEX instance. It’s possible to allow any N2148T to connect to any FEX instance defined on a N5k. Simply plug in the N2k and off it goes.

This is a good low-maintenance approach, but what if I want to be more granular? What if I have several N2ks and I want to ensure that each N2k is plugged into the correct interfaces on the N5k? The only way to verify this is to tie a serial number to the FEX ID on the N5k, which will only allow that single N2k to come up on that FEX ID… or will it? What happens if the wrong serial number is entered?
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Methods for connecting FEXs

January 29th, 2010

If you’re wondering what an FEX is, check out this article:

FEXs are connected to the parent switch(es) via fabric interfaces.  These are 10Gbps interfaces which connect the two switches (think of a stacking cable on a 3750-series switch).

There are two methods of configuring fabric interfaces:

  • Static pinning
  • EtherChannels

Although these are somewhat differentiated in some of the documentation, the static pinning looks almost the same as that used for EtherChannels.  The main difference is that static pinning uses physical interfaces, whereas EtherChannel uses a single Port-Channel interface for the fabric interface (there are some minor configuration differences and requirements as shown below).

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Introducing the Nexus 2148T (Fabric Extenders)

January 29th, 2010

The Nexus 5000-series (5010 and 5020) support the Nexus 2000-series of switches.  The Nexus 2000-series are fabric extenders (FEXs) – which is essentially a way to stretch out the N5k switch fabric.  Currently there’s only the Nexus 2148T switch, which we’ll cover (at least the basics) in this article.

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NX-OS – great interface range support

January 29th, 2010

(as I’ve been working with NX-OS as of late, I decided to jot down some thoughts and findings – this is one part in a series of posts on NX-OS)

Have you ever visited a friend’s house and said “I like what you’ve done with the place!”  Many of us have – in which case you should be able to relate to this post.  There are moments in working with NX-OS where I want to tell Cisco “I like what you’ve done with the place!”  This post is about just such a finding — the great support of interface ranges within NX-OS.

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Netsh IPv6 cheat sheet

January 28th, 2010

This is a short post, which may not add a lot of value (hopefully it’s helpful at least a little).  While attending an IPv6 training session, netsh was referred to and I started looking at it.  I haven’t done a lot with IPv6 up to this point, so haven’t been familiar with the plenitude of information available within netsh.

Well, I started to play around with netsh and was somewhat overwhelmed by the number of commands.  After messing around with it for awhile, I found that most of the commands provided little (if any) benefit to me, however the following commands looked like they’d be useful, so I decided to jot them down.

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