Show 155 – Integrating OTV, FabricPath & LISP – Sponsored

At Cisco Live 2013 in Orlando, Packet Pushers co-hosts Ethan Banks and Greg Ferro sat with Nexus 7000 champion Ron Fuller and network design expert Russ White to discuss how, when and why you might choose to deploy FabricPath, OTV, or LISP. In particular, we get into the specifics of what each protocol does, where […]

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Ethan Banks

Co-host at Packet Pushers

Ethan Banks, CCIE #20655, has been managing networks for higher ed, government, financials and high tech since 1995. Ethan co-hosts the Packet Pushers Podcast, which has seen over 3M downloads and reaches over 10K listeners. With whatever time is left, Ethan writes for fun & profit, studies for certifications, and enjoys science fiction. @ecbanks
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The post Show 155 – Integrating OTV, FabricPath & LISP – Sponsored appeared first on Packet Pushers Podcast and was written by Ethan Banks.

IGP Metric Tweaks – Direction is Important

A while back I was responsible for setting up a group of switches and routers to serve as the internet distribution for a hospital, mainly the function of designing the IGP of choice to work given the hospital’s requirements and coordinating with the teardown of the old gear. The idea was to configure EIGRP so that one next-hop was preferred over another. We know this is possible through tweaking the various metrics for a given IGP, but in the process, I was reminded of something that’s quite important to think about when doing so.

IGP Metric Tweaks – Direction is Important

A while back I was responsible for setting up a group of switches and routers to serve as the internet distribution for a hospital, mainly the function of designing the IGP of choice to work given the hospital’s requirements and coordinating with the teardown of the old gear. The idea was to configure EIGRP so that one next-hop was preferred over another. We know this is possible through tweaking the various metrics for a given IGP, but in the process, I was reminded of something that’s quite important to think about when doing so.

IGP Metric Tweaks – Direction is Important

A while back I was responsible for setting up a group of switches and routers to serve as the internet distribution for a hospital, mainly the function of designing the IGP of choice to work given the hospital’s requirements and coordinating with the teardown of the old gear. The idea was to configure EIGRP so that one next-hop was preferred over another. We know this is possible through tweaking the various metrics for a given IGP, but in the process, I was reminded of something that’s quite important to think about when doing so.

Healthy Paranoia Show 15: The Dudes of REN-ISAC

It’s the latest dudilicious episode of Healthy Paranoia! This time we’ll be covering the topic of information sharing and analysis centers (ISAC), specifically in the research and educational networking sector, aka REN-ISAC. Joining Mrs. Y on this adventure into the land of dudeness is Wes Young, REN-ISAC Principal Security Engineer and Architect (El Duderino), Keith […]

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Mrs. Y

Snarkitecht at Island of Misfit Toys

Mrs. Y is a recovering Unix engineer working in network security. Also the host of Healthy Paranoia and official nerd hunter. She likes long walks in hubsites, traveling to security conferences and spending time in the Bat Cave. Sincerely believes that every problem can be solved with a "for" loop. When not blogging or podcasting, can be found using up her 15 minutes in the Twittersphere or Google+ as @MrsYisWhy.
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The post Healthy Paranoia Show 15: The Dudes of REN-ISAC appeared first on Packet Pushers Podcast and was written by Mrs. Y.

Lessons Learned Writing a Custom Config Builder

A while back, I set about developing a modest configuration templating system for my employer. When I first joined the company, new network devices were being provisioned using configuration templates stored as Microsoft Word files, which, as you can imagine, was pretty painful. Each variable had to be identified and replaced by hand in a tedious and error-prone process. I wanted something better, but also cheap (or free) and simple. So I started building something.

To kick off my crazy project, I first decided to build a web application based on the Django Python framework (the same platform on which PacketLife.net runs). Django and similar frameworks handle most of the mundane tasks involved in writing a web application and allow for rapid prototyping. It also includes a built-in administration interface for creating and manipulating data independent of the front-end user interface. I spun up a modest internal VM running...

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You got promoted, now what?

Leadership in most companies is not really something explicitly practiced. Generally, a few people who are naturally inclined kind of do their thing while the rest of the leadership ranks sort of ignore the finer points of people management. But why is that the case? And how do you avoid being one of those leaders […]

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Michael Bushong

The post You got promoted, now what? appeared first on Packet Pushers Podcast and was written by Michael Bushong.

Confusing The Familiar with The Superior

We all know the archetype of the fanboy (or fangirl of course, however I will forthwith use zealot as a gender-neutral term). They expound upon the superiority of their favorite… whatever, and lambaste the competing product or products, and will hear of nothing that would contradict their conclusions. The battle the zealots fight are well known: […]

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Tony Bourke

Tony Bourke is an IT instructor teaching Cisco and other courses for various organizations. He writes about the hilarity of the converged roles at datacenteroverlords.com and random musing on twitter @tbourke. He's also an amateur pilot, skydiver, scuba diver, marathon runner, and crazy cat lady.

The post Confusing The Familiar with The Superior appeared first on Packet Pushers Podcast and was written by Tony Bourke.

PQ Show 30 – RPKI DNSEC and Internet Security with Ivan Pepelnjak

There are two proposals floating around that are trying to address BGP origination hijacks (aka Pakistan vs. YouTube): RPKI and DNSSEC-based system. Ivan Pepelnjak joins Greg Ferro to talk about what is means for Networking. This show was recorded in January 2013 and it’s been delayed publishing. Please accept my apologies. Show Links Opinionated background […]

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Greg Ferro

Greg Ferro is a Network Engineer/Architect, mostly focussed on Data Centre, Security Infrastructure, and recently Virtualization. He has over 20 years in IT, in wide range of employers working as a freelance consultant including Finance, Service Providers and Online Companies. He is CCIE#6920 and has a few ideas about the world, but not enough to really count.

He is a host on the Packet Pushers Podcast, blogger at EtherealMind.com and on Twitter @etherealmind and Google Plus.

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The post PQ Show 30 – RPKI DNSEC and Internet Security with Ivan Pepelnjak appeared first on Packet Pushers Podcast and was written by Greg Ferro.

Quality of Service (QoS) Congestion-Avoidance Notes

Congestion-avoidance tools are complementary to, and dependent upon, queuing algorithms. Queuing/scheduling algorithms manage the front of a queue, while congestion-avoidance mechanisms manage the tail of a queue.

Congestion-avoidance tools are designed for TCP traffic, because TCP has built-in flow-control mechanisms that operate by gradually increasing traffic flows until packet loss has occurred.  Once packet loss has occurred, the transmission rate is reduced before slowly ramping up again.  This means that if no mechanism is in place to control TCP, any particular flow has the ability to eat up all available bandwidth.

When there are no congestion-avoidance tools in place, and queues fill, tail drop occurs, which means all traffic is dropped. 

In a constricted channel without congestion-avoidance tools, TCP connections eventually synchronize with each other – they ramp up together, lose packets together, and back off together.  This is called global synchronization and basically results in “waves” of TCP traffic.

Congestion-avoidance tools has no real benefit or use for UDP traffic, because UDP traffic does not have any retry logic.

Random Early Detection (RED)

RED combats global synchronization by preemptively and randomly dropping packets before queues fill.  Instead of waiting for the queues to fill, Continue reading

Calculating distances in meatspace

I'm working on an automated provisioning system for a very large VPN network. For each new VPN client, I need to select a headend site where VPN tunnels should land. The only data available is that which I can get from the sales and billing systems. This system offers me the zip code of the install site.

Using the zip code of the install site, and the known zip codes of my various head-end sites, I'm able to select the destination for the primary and secondary VPN tunnels.

It's not perfect (physical location often has little to do with network path), but it's better than nothing. I haven't decided how to handle non-US sites yet.

I'm using a database of US zip codes found here, and a very dirty perl script. The script grabs the latitude and longitude of two zip codes from the database, and prints the mileage between them as calculated using the Haversine formula for great circle distance.

It runs like this:


Christophers-MacBook-Pro:scripts chris$ zipdistance.pl 95134 60614
1837 miles
Christophers-MacBook-Pro:scripts chris$

The script:


#!/opt/local/bin/perl
use GIS::Distance;

my $dbfile="/Users/chris/Downloads/zipcode.csv";
my $lat1,$lon1,$lat2,$lon2;

sub usage{
  printf "Usage: $0 <zipcode> <zipcode>n";
  exit;
}

if (@ARGV ! Continue reading

The value of Connectors in the workplace

In Malcolm Gladwell’s book The Tipping Point [affiliate link] the author identifies key roles that individuals play in spreading knowledge and ideas. Gladwell outlines two key roles, the maven and the connector. The maven is a person who accumulates subject matter expertise and is willing to distribute that knowledge on request. Think of a maven […]

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John Harrington

John is an experienced data center engineer with a background in mobile telecoms. He works as a network test engineer for a large cloud service provider, and is gradually accepting that he's a nerd. He blogs about network technology and careers at theNetworkSherpa.com. You can reach him on twitter at: @networksherpa

The post The value of Connectors in the workplace appeared first on Packet Pushers Podcast and was written by John Harrington.

Ageism and your career in I.T.

I recently decided to commit to my current company.  I don’t mean work harder or focus more, though that’s implicit.  I mean to consider being a “lifer.”  For an independent personality like myself that’s a pretty tall leap.  One of the reasons I got my CCIE was to avoid ever being the guy sweating when […]

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Keith Tokash

Keith Tokash

Keith Tokash, CCIE (R&S) #21236, began his career in 1999, and has spent the last decade running around large content and small ISP networks. He spends his spare time with his newborn son, on the mat at the local Jiu-Jitsu gym, and trying to keep his fat yap shut.

The post Ageism and your career in I.T. appeared first on Packet Pushers Podcast and was written by Keith Tokash.

Software Defined Data Centres and the blending of cultures

As some of you may know, I have spent a fair amount of my time in the last few years designing and improving multi-tennant hosting environments. Each revision attempts to learn from the mistakes of the previous iterations, as well as bundle in new features and “advancements” from each of the different vendors in the stack.

New offerings on the storage fronts, developments in the server space in the form of the boom of virtualisation, and the simple existence of the network amongst the fact that none of these technologies changed the existing/fundamental laws of networking.

Software-Defined Networking has sprung up as a way of providing both advancements in our current architectures and providing agility in changes needed in the future, but what is truly needed is a true abstraction of the entire data centre model that encompassed all of compute, storage, security and networking. The ability to define all of the requirements of your existing data centre and have them deployed and rolled out across which ever stack you are using (Private / Public / Hybrid / Tomorrows Favourite buzz.), in a consistent and definable manner.

Merging the requirements of each of the existing silos and describing Continue reading

AdaptingIT: Why I Started a Podcast Featuring Women in Tech

As a systems admin a few years back I decided that I needed to figure out a way to understand networking.  I could do basic things, but how do you figure out what you don’t know?  That’s when I started listening to podcasts.  The first podcast I came across was Packet Pushers and I haven’t […]

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Lauren Malhoit

Lauren Malhoit

The post AdaptingIT: Why I Started a Podcast Featuring Women in Tech appeared first on Packet Pushers Podcast and was written by Lauren Malhoit.

When it’s OK to say “No”

A lot of us struggle in our careers when it comes to accepting or declining work, whether it be voluntary or voluntoldary. Especially the individuals in our field that strive to succeed. We see it as another opportunity to stand up to the plate and knock one out of the park. The problem, however, is that […]

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Edward Henry

Edward Henry is currently employed with a regional optical network concentrating on Research and Education within the communities of Connecticut. Along with his day job, Edward is an avid techy and has been working toward advancing his career with all things nerdy. Also follow Ed on Twitter : @NetworkN3rd and at his personal blog : https://networkn3rd.wordpress.com

The post When it’s OK to say “No” appeared first on Packet Pushers Podcast and was written by Edward Henry.

Cisco UCS vNIC Switchport Mode

I wrote an article a while back regarding VLAN configuration when running vSphere ESXi on top of Cisco UCS. A comment pointed out that all vNICs are automatically configured as trunks. I had not heard of this before, so I got into the CLI to take a look. Here’s a VLAN configuration screen in the UCSM GUI for a sample vNIC: Check out the running configuration for this vNIC on the underlying NX-OS CLI.

Cisco UCS vNIC Switchport Mode

I wrote an article a while back regarding VLAN configuration when running vSphere ESXi on top of Cisco UCS. A comment pointed out that all vNICs are automatically configured as trunks. I had not heard of this before, so I got into the CLI to take a look. Here’s a VLAN configuration screen in the UCSM GUI for a sample vNIC: Check out the running configuration for this vNIC on the underlying NX-OS CLI.

Network Toolkit

My case full of network doodads always generates lots of questions when people see it for the first time. I don't carry dedicated iPhone chargers anymore, but Apple cube chargers forgotten behind hotel nightstands is where this started.

With this kit it is immediately apparent when something is missing, so things tend to not get left behind.

The limited space has driven me to find the best and most compact solutions to all of my problems. I'm really pleased with everything that's in here. I'm also aware that it's super nerdy.


The case itself is a Duluu Essential case for iPad. It's a nice semi-rigid clamshell type case. I've made two modifications:

  1. Removed the padded "page" between the two halves. This thing was intended to keep the stuff in the pockets on the left from scratching the iPad on the right. It also served as an iPad stand.
  2. I removed the original zipper pulls, replaced them with a repair part because the square corners of the original pulls tended to cause problems.
On the right side of the case I've installed a bit of floor padding foam (this kind of thing, but mine came from Harbor Freight Tools), Continue reading
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