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Excerpt: There are a million articles out there on ESXi vSwitch Load Balancing, many of which correctly point out that the option for routing traffic based on IP Hash is probably the best option, if your upstream switch is running 802.3ad link aggregation to the ESXi hosts. It offers minimal complexity, while also providing the best load-balancing capabilities for network devices utilizing a vSwitch (Virtual Machine OR vmkernel). So…this article will be catered towards a very specific problem. Symptoms Since this post was inspired by an experience of mine, I will briefly explain the problem symptoms that surfaced as a result of incorrect…
ESXi vSwitch Load Balancing Woes
May 21, 2013 by Leave a Comment
Open Source Switching
May 9, 2013 by Leave a Comment
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Excerpt: There’s been a ton of attention lately around the concept of using commodity hardware in an area of the industry that is currently dominated by proprietary ASIC-based solutions – networking. When it comes to crossing paths between open source and networking, the obvious low-hanging fruit has been software-based switching solutions like Open vSwitch, or cool ways to make virtual switching do bigger, better stuff for cloud providers like Openstack Quantum (awesome, by the way). For those that follow me online at all, you know I’ve been on a virtual routing kick lately – just another sign that performing network functions…
Routing iSCSI Traffic
April 23, 2013 by 2 Comments
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Excerpt: This post was initiated by a side conversation I had about iSCSI. From time to time I’m required to implement an iSCSI-based solution, and this is not the first time I’ve heard the question: “So why can’t I route iSCSI traffic?” Most folks with any knowledge of storage protocols will have at some point picked up this informal best practice idea; some will vehemently defend this idea as the word of $deity and shun all those who contradict this truth. Disclaimer: this post is based on my experience. I realize (and hope) this may kick off some debates – just keep…
Using GNS3 for Switching Labs
February 13, 2013 by 3 Comments
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Excerpt: For so long, I’ve heard – as have many of you I’m sure – that GNS3, though a GREAT emulator for Cisco IOS software, is not practical for studying anything related to switching. Routing is handled just fine, but because of the proprietary ASICs in Cisco switches, it is not something that can be easily reverse-engineered, thus GNS3 cannot do it. After all, all routing is essentially done in software in GNS3. I actually wrote this article in part over a year and a half ago, but these concepts still hold up, and I decided to get it out of drafts…
TCP Handshakes, Routing, Hairpinning – Oh My!
January 28, 2013 by Leave a Comment
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Excerpt: I’m working on setting up a lab that consists of leading storage and compute products for testing, and I ran into some interesting issues with a few different things…some with respect to the way the Cisco ASA does hairpinning, as well as allowed connections in such a configuration. There were also some routing issues experienced as a result, and I want to explore my experience in all of this during this post. I encourage you to lab this up in GNS3 – you will learn a lot about the basics of TCP as well as routing. First off, the overall…
Quality of Service [Part 1]: Types of QoS Policies
November 7, 2012 by 3 Comments
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Excerpt: There’s a lot of information out there about QoS and it’s an area where I’m only now starting to feel comfortable. I’ve been fortunate enough to have a decent amount of experience configuring datacenter equipment, especially in the context of a Flexpod, so I’ve been forced to know how all of these technologies play together with respect to QoS, which is very important when running sensitive applications like voice on such an infrastructure. I’d like to kick off a multipart series (I have three articles planned at the time of this writing) where we explore certain aspects of QoS and how…
Spanning-tree Requirements for Cisco ISSU
September 19, 2012 by 2 Comments
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Excerpt: I had a great conversation with a coworker regarding the requirements for the In-Service Software Upgrade (ISSU) feature on Cisco switches. For this post, I’m using Nexus 5548UP switches as a distribution layer to my Cisco UCS environment, and at the core is sitting a pair of Catalyst 6500s, set up in a VSS pair. For those unfamiliar with ISSU, it is a way for Cisco devices to upgrade their running firmware without the need for a disruptive reboot of the device, which is what has traditionally been used for upgrades to IOS, NX-OS, etc. This is obviously a good thing,…
