Category Archives: Data Center

L3 vPC Support on Nexus 5k

So… I’m a little embarrased to admit this but I only very recently found out that there are significant differences in how Virtual Port Channels (vPC) behave on the Nexus 5k vs the Nexus 7k when it comes to forming routing adjacencies over the vPC.

Take the title literally!
Take the title literally!

I’ve read the vPC Best Practice whitepaper and have often referred
others to it and also referred back to it myself from time to time. What I failed to realize is that I should’ve been taking the title of this paper more literally: it is 100% specific to the Nexus 7k. The behaviors the paper describes, particularly around the data plane loop prevention protections for packets crossing the vPC peer-link, are specific to the n7k and are not necessarily repeated on the n5k.

Continue reading L3 vPC Support on Nexus 5k

NSF and GR on Nexus 5000

NSF and GR are two features in Layer 3 network elements (NEs) that allows two adjacent elements to work together when one of them undergoes a control plane switchover or control plane restart.

The benefit is that when a control plane switchover/restart occurs, the impact to network traffic is kept to a minimum and in most cases, to zero.

Continue reading NSF and GR on Nexus 5000

Avoiding an ISSUe on the Nexus 5000

The idea for this post came from someone I was working with recently. Thanks Fan (and Carson, and Shree) :-)

In Service Software Upgrade (ISSU) is a method of upgrading software on a switch without interrupting the flow of traffic through the switch. The conditions for successfully completing an ISSU are usually pretty strict and if you don’t comply, the hitless upgrade can all of a sudden become impacting.

The conditions for ISSU on the Nexus 5000 are pretty well documented (cisco.com link) however, there are a couple bits of knowledge that are not.  This post is a reminder of the ISSU conditions you need to comply with and a call out to the bits of information that aren’t so well documented.

Continue reading Avoiding an ISSUe on the Nexus 5000

Speaking Notes: The Data Center Network Evolution

I will be presenting at the Cisco Connect Canada tour in Edmonton and Calgary on November 3rd and 5th, respectively. My presentation is about that three letter acronym that everyone loves to hate: SDN :-)

I will talk about SDN in general terms and describe what it really means; what we’re really doing in the network when we say that it’s “software defined”. No unicorns or fairy tales here, just engineering.

Next I’ll talk about three areas where Cisco is introducing programmability into its data center solutions:

  • Application Centric Infrastructure
  • Virtual Topology System
  • Open NX-OS

Below are the notes I made for myself while researching these topics and preparing for the presentation. At the bottom of this post is a Q&A section with some frequently asked questions.

Continue reading Speaking Notes: The Data Center Network Evolution

Five Functional Facts about VXLAN

It seems appropriate to write a FFF post about Virtual Extensible LAN (VXLAN) now since VXLAN is the new hotness in the data center these days. With VMware’s NSX using VLXAN (among other overlays) as a core part of its overall solution and the recent announcement of Cisco’s Application Centric Infrastructure (ACI) and the accompanying Nexus 9000 switch, both of which leverage VXLAN for delivering a network fabric, it seems inevitable that network engineers will have to use and understand VXLAN in the not too distant future.

As usual, this post is not meant to be an introduction to the technology; I assume you have at least a passing familiarity with VXLAN. Instead, I will jump right into 5 operational/technical/functional aspects of the protocol.

For more information on VXLAN, check out the draft at the IETF. Continue reading Five Functional Facts about VXLAN

Five Functional Facts about OTV

Following on from my previous “triple-F” article (Five Functional Facts about FabricPath), I thought I would apply the same concept to the topic of Overlay Transport Virtualization (OTV). This post will not describe much of the foundational concepts of OTV, but will dive right into how it actually functions in practice. A reasonable introduction to OTV can be found in my series on Data Center Interconnects.

So without any more preamble, here are five functional facts about OTV.

Continue reading Five Functional Facts about OTV

DCI with LISP for Cold Migrations

Let’s step back for a minute. So far in this series of blog posts on DCI, I’ve been focusing on extending the Layer 2 domain between data centers with the goal of supporting hot migrations — ie, moving a virtual machine between sites while it’s online and servicing users.

Is that the only objective with DCI? Continue reading DCI with LISP for Cold Migrations

Cisco onePK: Now I Get It

I had an opportunity recently to sit in a Cisco onePK lab and it opened my eyes to exactly what Cisco is doing with onePK, why it’s going to be so important as Software Defined Networking (SDN) continues to gain traction, and why onePK is different than what anyone else is doing in the industry.

onePK is a key element within Cisco’s announced Open Network Environment SDN strategy. onePK is an easy-to-use toolkit for development, automation, rapid service creation and more. It enables you to access the valuable data inside your network via easy-to-use APIs.

Source: www.cisco.com/go/onepk

Since having my own eyes opened, I’ve been pondering how to explain my new found understanding in a way that others will grasp. In particular to business decision makers (BDMs) and technical decision makers (TDMs). I’m really, really, struggling to come up with a good analogy for BDMs. I’m still working on that one. Surprisingly, I’m also struggling to come up with a sound analogy that will work with the majority of TDMs that I know. Maybe I shouldn’t be so surprised at that since all the TDMs I deal with are on the infrastructure side of things (networks, storage, compute, platform) and really don’t deal with software. There’s a gap there that I somehow need to bridge. I’m still pondering how to successfully do that.

However, there is a slice of the TDM population that I believe I can reach right now. These folks, like myself, have software and network experience. Maybe through open source projects, previous careers, or just mucking about with LAMP stacks in their own lab/home network, they understand programming semantics, APIs, and extending the functionality of third-party software.

I’m going to use a popular open source software package to draw some parallels with what Cisco onePK will soon allow organizations to do to their networks. Continue reading Cisco onePK: Now I Get It

An Introduction to the Nexus 7700

We’re halfway through 2013 and we have our second new member of the Nexus family of switches for the year: the Nexus 7700. Here are the highlights:

  • Modular, chassis-based system
    • 18 slot (16 IO modules) and 10 slot (8 IO modules)
  • True front-to-back airflow
  • New fabric modules
    • (6) fabric modules (maximum) per chassis
    • 220G per slot per fabric module
    • 1.32Tbps per IO module slot
  • Supports F2E and newly announced F3 IO modules Continue reading An Introduction to the Nexus 7700

DCI: Using FabricPath for Interconnecting Data Centers

Here’s a topic that comes up more and more now that FabricPath is getting more exposure and people are getting more familiar with the technology: Can FabricPath be used to interconnecting data centers?

For a primer on FabricPath, see my pervious article Five Functional Facts about FabricPath.

FabricPath has some characteristics that make it appealing for DCI. Namely, it extends Layer 2 domains while maintaining Layer 3 – ie, routing – semantics. End host MAC addresses are learned via a control plane, FP frames contain a Time To Live (TTL) field which purge looping packets from the network, and there are no such thing as blocked links – all links are forwarding and Equal Cost Multi-Pathing (ECMP) is used within the fabric. In addition, since FabricPath does not mandate a particular physical network topology, it can be used in spine/leaf architectures within the data center or point-to-point connections between data centers.

Sounds great. Now what are the caveats? Continue reading DCI: Using FabricPath for Interconnecting Data Centers