Writing

Technology

Technical articles, tutorials, and insights on modern technology topics.

All Posts

Complete chronological list of all blog posts and articles.

The Shortsighted Expansion of Timber Production: A Dangerous Executive Order

March 4, 2025 · jtdub.com politics analysis

On March 1, 2025, President Trump issued an executive order aimed at rapidly expanding timber production in the United States. This order seeks to streamline permitting processes, increase timber harvesting, and boost domestic timber production by allowing for the accelerated removal of trees from national forests. The policy is being touted as a way to create jobs, reduce dependency on foreign timber imports, and improve forest management, all while lowering construction costs. However, the potential...

Comparing Javier Milei and Bill Clinton's Balanced Budget Strategies: Lessons for the U.S.

February 26, 2025 · Essays jtdub.com politics

In the world of fiscal policy, balanced budget strategies are often central to the economic philosophies of politicians and administrations.: post title: “Comparing Javier Milei and Bill Clinton’s Balanced Budget Strategies: Lessons for the U.S.” date: ‘2025-02-26’ author: jtdub tags: jtdub.com politics analysis

It's Time to Write Your Representatives - February 2025

February 2, 2025 · Essays jtdub.com politics

There is significant turmoil in the United States due to the actions of the Trump administration and the rapid developments unfolding. Some of these actions are illegal and pose a constitutional crisis. I’ve created a template to help you clearly articulate your concerns to your representatives.

Understanding Dataloaders in AI: What They Are and Why They Matter

February 2, 2025 · packetgeek.net python Open Source

In the realm of artificial intelligence (AI) and machine learning (ML), dataloaders play a critical role in managing data efficiently during model training and evaluation. This blog will delve into what dataloaders are, their importance, and how to use them in popular frameworks like PyTorch and TensorFlow.

25 Years of U.S. Oil Dynamics: A Deep Dive into Production, Consumption, and Trade

January 27, 2025 · Essays jtdub.com data is beautiful

Over the past quarter-century, the U.S. oil industry has undergone profound transformations, shaped by technological breakthroughs, economic forces, policy shifts, and global market dynamics. This blog explores the key trends in oil production, consumption, imports, and exports, with a focus on the most recent developments.

PCAP or It Didnt Happen

January 25, 2025 · packetgeek.net MPLS PCAP

In the world of IP networking, everything boils down to packets. Without a solid understanding of how packets are structured, diagnosing issues, optimizing performance, or even designing a robust network can feel like shooting in the dark. That’s why understanding packet structures isn’t just helpful—it’s essential.

What Are Tokenizers in AI, and Why Are They Important?

January 24, 2025 · packetgeek.net python Open Source

Artificial intelligence (AI), especially in the realm of natural language processing (NLP), revolves around the ability of machines to understand and generate human language. However, computers do not inherently understand words the way humans do. This is where tokenizers come into play—a crucial mechanism in bridging the gap between human language and machine-readable formats.

Hierarchical Configuration Version 3

December 11, 2024 · packetgeek.net python hier_config

Introduction

Predicting Future Internet Capacity Needs Using Time Series Data

November 24, 2023 · packetgeek.net python pandas

In the era of digital transformation, efficient management of internet bandwidth is crucial for both individuals and businesses. As we become increasingly reliant on the internet for our daily activities, predicting future internet capacity needs is no longer just desirable—it’s essential. This blog post will guide you through the process of consuming your internet bandwidth time series data from your network monitoring platform to predict your future capacity needs.

The Despacho Ceremony: An Ancient Andean Tradition

May 13, 2023 · Essays jtdub.com anthropology

The Despacho ceremony is a cornerstone of Andean culture, a sacred ritual ingrained in the indigenous communities of Peru, Bolivia, Ecuador, and Colombia. It is a vibrant celebration of gratitude, balance, and harmony, reflecting the profound connection these cultures have with the natural world and spiritual realm.

Extracting Specific Key-Value Pairs from a List of Dictionaries in Ansible

May 13, 2023 · packetgeek.net ansible python

Have you ever encountered a situation in Ansible where you had a list of dictionaries, each representing an item with multiple attributes, and you needed to extract only specific key-value pairs while keeping the rest of the data hidden? Such as wanting to specific data from a list of dictionaries that contains secrets that you did not want logged in Ansible stdout or stderr, but also did not to use no_log, making troubleshooting difficult? This...

RHCSA Version 8: Operating Running Systems

January 30, 2022 · packetgeek.net RHCSA Study Notes Linux

Boot, reboot, and shut down a system normally

RHCSA Version 8: Getting Started

January 10, 2022 · packetgeek.net RHCSA Study Notes

I plan on earning at least an RHCSA again this year, since I’m currently in a role that requires more Linux skills. I previously had an RHCE for version 6, but it has long expired. Since I more or less know what to expect, I believe most of the studying will be a brush up of what I already know. However, I do plan on creating a blog for every major section of the exam...

2019: Year in Diving

January 9, 2020 · Essays jtdub.com

I did a 2018 video and I enjoyed being a bit nostalgic of the years diving activities. I decided to do another one. Enjoy.

Archaeology Career Prospects

December 11, 2019 · Essays Research Archaeology

Anthropology is the study of people and cultures from present day to the earliest humans. There are many disciplines in anthropology, including archaeology. Archaeology is the study of past peoples and cultures through the material remains that they leave behind. These remains are called artifacts. Artifacts are any physical items that are created or used by people. This essay takes a look at the archaeology job marketplace. This essay will analyze the education requirements for...

A Tale of Incan Apu's and Climate Change

November 11, 2019 · Apu Pumasillo Peru 2019

My First Ultra Marathon

April 28, 2019 · Essays Trail Running Colorado Bend State Park

Group Trail Run at Colorado Bend State Park

April 22, 2019 · Trail Running Colorado Bend State Park Running

This past weekend, I led a group of trail runners, “Austin Dirt Runners”, on a ten mile tour of Colorado Bend State Park. We had an amazing time. Despite it being easter weekend, we got to the park early enough to beat the crowds. By the time we completed our run, the crowds started showing up. It was perfect.

2018 Diving Highlights

December 29, 2018 · Essays August Spring Cave Diving

It’s been an interesting year of diving. I haven’t done the most dives this year, but the dives that I’ve done have been interesting. I put together a short video showing some of the highlights.

Winter 2017 - Mexico Cave Diving

December 27, 2017 · Cave Diving Mexico 2017 Photography

Recently, some friends and I spent some time cave diving in Mexico. We had an excellent time, diving some new caves and some old caves. Below is a short video.

Sibinacocha Aerial View

November 10, 2017 · Photography Sibinacocha Aerial Photography

Laguna Sibinacocha is a stunningly beautiful place. It has clear blue waters, stunning mountain landscapes, glaciers, springs, scattered Incan artifacts, and amazing night sky’s. It’s certainly one of my favorite places.

Blue Lagoon, October 2017

November 9, 2017 · Blue Lagoon Photography Scuba Diving

Some friends and I met up at Blue Lagoon in Huntsville, TX. The goal of the dives were to do some skills before my friend started his GUE Tech 1 class. While my friends did skills, I took some pictures.

Spring Lake, September 2017

November 6, 2017 · Photography Scuba Diving Underwater Photography

My friend, Jennifer Idol and I recently did a dive at Spring Lake. We mostly had the place to ourselves. The sun was bright and the conditions were excellent.

Expedition Packing

August 14, 2017 · Expedition Sibinacocha Scuba Diving

Today, some friends and I set off on an expedition to the Peruvian Andes, where we’ll be exploring a remote mountain lake - above water and below water. During the trip, it’s my goal to keep a video log each day describing what has been happening during the trip. To wet the appetite, here is a quick video of packing for the trip.

A New Approach to Defending Against DDoS Attacks

October 21, 2016 · network security DDoS Security

DDoS (Distributed Denial of Service) attacks are getting larger, more sophisticated, and more pervasive. Just today (October 21, 2016), DDoS attacks against Dyn, Inc have impacted the availability of sites such as Twitter, Netflix, Github, and Spotify.

Network Lifecycle Management with Hierarchical Configuration

July 8, 2016 · Cisco Administration Python Scripting Python Tips Network Programmability

In a previous blog, I hinted at a network configuration life cycle management library called hierarchical_configuration. I’ve been meaning to write about it for a while, but we’ve been super busy at work. I also wanted to ensure that we get our latest version of the library out in the public for general consumption before I wrote about it.

Multi Change and Netlib Updates

June 22, 2016 · Cisco Administration Python Scripting Python Tips Network Programmability

I’ve implemented some new changes to pyMultiChange and netlib. The biggest change affects both netlib and pyMultiChange. In netlib, I ripped out both the ‘simple_creds’ and ‘simple_yaml’ methods, as both stored user credentials in plain text on the computer that you used them on.

Kicking the tires on the new Ansible Network Modules, Part 2

March 1, 2016 · Python Tips Network Programmability DevOps

In the previous blog, I kicked the tires on the ios_command and ios_config Ansible modules. I still had my development environment set up from then, so I decided that I wanted to kick the tires on the ios_template module.

Kicking the tires with the new Ansible Network Modules

February 29, 2016 · Python Tips Network Programmability DevOps

Ansible recently announced support for multi-vendor network modules, natively within Ansible. There are many examples on the Internet where individuals have taken the initiative to create their own modules to work with their favorite vendor. Some of these examples are Arista supplied modules, NX-OS modules created by Jason Edelman, NTC, and NAPALM. While these are all good, it’s nice to see that Ansible is taking some initiative to create some native functionality.

Using a serial console on Mac OS X

February 15, 2016 · Serial Console Mac OS X

As a network engineer, a fundamental task is putting a base configuration onto a device via a serial console. In Windows, there are several applications from Hyper Terminal to Putty. In Linux, there is minicom. I’ve never been a Microsoft fan, but have been a Linux user for many years. Over the last few years have been using Mac OS X full time for work and personal. Given this, I need the ability to access...

NANOG 66

February 15, 2016 · Data Center Network Programmability DevOps

NANOG 66 took place a couple weeks ago. Video’s and presentations are trickling on the Internet. Here are the list of video’s and presentations that I found particularly interesting:

Using Ansible to update your Home Dynamic DNS via Rackspace Cloud DNS

January 29, 2016 · DevOps Ansible packetgeek.net

Like most home Internet users, my home Internet has a dynamic IP Address. For many years, I used DynDNS to keep a hostname associated to my home Internet, so that I could access my home resources remotely. After DynDNS started charging for the service, I just created a sub-domain off one of the domains that I own. The problem has always been that I would only find out about my IP Address changing after a...

Using Ansible to PUSH Cisco IOS Configurations

August 29, 2015 · Cisco Administration Python Scripting IOS Python Tips

There are a lot of very good articles on the Internet about how Network Engineers can use Ansible to create standardized network device configurations or use Ansible with existing network vendor API’s to make changes to network devices. Some of my favorites can be found on the Python for Network Engineers and Jason Edelman’s sites.

pyMultiChange rewrite and Netlib

August 26, 2015 · Cisco Administration Python Scripting Python Tips packetgeek.net

I re-wrote ‘pyMultiChange’ around my new library for connecting and managing devices. Before I was using ‘pyRouterLib’, but now I’ve deprecated that library with the creation of my new library ‘netlib’.

Dockerizing IOS-XRv

April 5, 2015 · Linux Software Defined Networking Miscellaneous Hacking

I’ve been playing with docker off and on for about a year or so now. One of my ideas, with Docker, is to use it for my network lab. These days, I’ve mostly virtualized my lab. Lately, been doing a lot of it in VIRL, but this hasn’t stopped me from tinkering.

Troubleshooting Internet Connectivity

March 12, 2015 · troubleshooting Network Connectivity Rackspace

This evening, I noticed that I was having some horrible Internet connectivity issues, from home. Trying to stream anything online? Forget it. Frustrated, I started troubleshooting the issue, fully expecting that I would end up opening up a trouble ticket with my ISP, sending them all my available troubleshooting information, and asking them to resolve their issue.

pyMultiChange and pyRouterLib Updates

February 2, 2015 · Cisco Administration Python Scripting Python Tips packetgeek.net

I recently had a request to combine the SSH and TELNET functionality on my pyMultiChange scripts, as they share a lot of code. I thought that this was a reasonable request, so I started that process today.

MPLS Control and Data Plane Cheat Sheet

December 8, 2014 · MPLS CCNP SP Study Notes IOS-XE

📚 Archived Content: This post is part of my historical study notes archive. While some concepts may remain relevant, the specific technologies, procedures, and certifications mentioned may be outdated. For current technical content, visit the Technology section.

Cisco VIRL Status? Digital Paper Weight

December 3, 2014 · Miscellaneous Hacking Cisco VIRL Misc.

Update: I fixed the issue. Turns out, I’m a dim wit. There is an updated post, with tips and lessons learned, here.

Cisco VIRL - Bare Metal Install Tips and Lessons Learned

December 3, 2014 · Linux Miscellaneous Hacking Cisco VIRL

In my first post on VIRL - ”Cisco VIRL Status? Digital Paper Weight”, I shared my frustration with not being able to get my system to activate with Cisco. Come to find out, I’m a dim wit. That is, in the ‘Salt ID and domain’ section, I mistakenly left the .pem suffix in the name. Ironically, I blurred out that section, in an attempt to retain some privacy. However, if I hadn’t somebody may have...

The Irony of Using SDN and NFV to Study Legacy Network Technologies

November 30, 2014 · packetgeek.net

I was recently asked to present at a local Network Engineering Meetup. The topic that I’m going to speak about is how I’m using KVM, OpenFlow, Network Overlays, and OVS to integrate my physical network lab and virtual network lab. The presentation can be found here.

Mental Note: Tracking L3 Glean Attacks

November 28, 2014 · network security IOS Routing Protocols

Here’s a handy debug command for tracking L3 Glean attacks on IOS based Cisco routers / L3 switches.

pyMultiChange - SSH Script Update

November 25, 2014 · Cisco Administration Python Scripting Software Defined Networking Python Tips

I updated the ssh-multi.py script from my pyMultiChange repository. It’s now fully functional and allows you to enter ‘enable’ mode on Cisco routers and switches. As I’m using the paramiko library to interact with routers and switches via SSH, I had to switch from using the ‘exec_command’ API to invoke_shell, send, and recv API’s. It took a little more work - and I’m not completely thrilled with how the ‘recv’ API is implemented in paramiko,...

Updated pyRouterLib and pyMultiChange

November 24, 2014 · Cisco Administration Python Scripting Software Defined Networking Python Tips

I’ve updated a two pieces of software that I’ve been writing and maintaining. The first is pyRouterLib. pyRouterLib is a library, written in Python, that takes the common functionality of managing a Cisco router or switch, via Python and makes it easy to implement.

Python with Multiple Threads

November 20, 2014 · Python Tips packetgeek.net

I have a need to have a script to execute the same task, among many devices, as close to the same time as possible. As a non-programmer, whom happens to write code in an effort to make my job easier, I thought the task would be easier than it actually is. Spawning multiple threads is pretty easy. However, hitting resource limits is a limiting factor - as is how you output your data.

Connecting Your Virtual IOS-XE and IOX-XR Lab To Your Physical Lab

October 1, 2014 · IOS Linux Software Defined Networking

Working with Cisco Routers and Switches with Python

July 27, 2014 · Cisco Administration Python Scripting System Administration Miscellaneous Hacking

I’ve updated the pyMultiChange.py script. It now is fully functional, with the addition of enable mode functionality. With this script, you can take a list of routers and switches from a text file and execute a series of commands, from a text file, all from SSH. For example:

Updating my Python Scripts to access Cisco Devices

July 26, 2014 · Cisco Administration Python Scripting Python Tips packetgeek.net

I’ve been working to migrate my python scripts, that access Cisco routers and switches to utilize SSH. I’m building out a ‘pyRouterLib’ class, that currently doesn’t have much functionality, but I’m going to be building it out a lot more in the coming months. I’m also working on my pyMultiChange script, so that it utilizes SSH as well. Currently, the work is going well, although, there is still more work to go.

Dynamic DNS Updates via the Rackspace Cloud DNS

July 26, 2014 · DNS Python Tips Bind

Do you remember the old days when dyndns.org offered free sub domains, that pointed to your home internet connection? This service allowed you to access your home computer remotely, by hostname, without the need of remembering your IP Address.

Linux Unified Key Setup

May 29, 2014 · LUKS Encryption packetgeek.net

Here are some notes that I took about setting up LUKS when studying for the RHCSA. I felt that this would be appropriate to post after the recent issues with TrueCrypt.

OSPF Area Types and LSA's

April 11, 2014 · OSPF CCNP SP Study Notes packetgeek.net

IOS-XR (XRv) and IOS-XE (CSR1000v) KVM Config Generation

April 5, 2014 · Innovative Virtualization Miscellaneous Hacking

CCNP - Service Provider - SPROUTE

April 4, 2014 · CCNP SP Study Notes packetgeek.net

TelnetCisco.py - A Reusable Module for Accessing Cisco Devices with Python

February 17, 2014 · Cisco Administration Python Scripting Python Tips packetgeek.net

For one reason or another, Python seems to have been my go to scripting language of choice recently. One of the things that I’ve been working on is creating a reusable python library for accessing Cisco devices via telnet. It’s pretty basic code right now, but I’ll be expanding upon what I have soon and will be sharing via github.com as well. For now, here is my simple library.

Quick intro to Puppet

February 9, 2014 · Linux Puppet packetgeek.net

I’ve been using puppet for a while to automate several things within the Linux servers that I manage. It’s also one of those things that if I don’t use it in a while, I forget it. So, I’m going to do a quick run through of registering a puppet agent with a puppet master. I’ll also show some of the things that every Linux install gets pushed, aka the default settings.

I'm going to place these here...

December 4, 2013 · VXLAN Innovative SDN

I found these articles fantastic and I wanted a quick place to reference them all. They are all in relation and deal with NVP, SDN, Open vSwitch, and VXLAN.

DMVPN with VRF's for the Internet interfaces and BGP

November 25, 2013 · DMVPN VRF BGP

I’ve been playing with some different DMVPN configurations. In this scenario, I wanted the Internet facing interface to have a separate routing table, which I accomplished with a VRF. I also wanted to use a phase 2 DMVPN - which allows spokes to communicate directly to each other without having to send all traffic to the hub. The tricky part was getting the DMVPN tunnels to form over that interface. This is accomplished via the...

Rackspace Performance vs Standard Cloud Server Disk I/O

November 22, 2013 · Filesystems Rackspace packetgeek.net

I just spun up a Rackspace High Performance Cloud Server and ran some i/o benchmarks on it and compared it to one of my standard cloud servers. Here are my findings.

Managing Cisco Routers / Switches with Python, Take 2

October 10, 2013 · Cisco Administration Python Scripting IOS System Administration

Here is my script to date. It’s functional and works pretty well, in my limited testing.

Configuring Cisco routers and switches with Python

October 8, 2013 · Cisco Administration Python Scripting IOS Python Tips

Update: I’ve updated the multichange script a lot since I first wrote about it. You can use the category function to see the various posts.

BGP Goodness and Links

September 25, 2013 · BGP packetgeek.net

I had my first real experience with playing with regular expressions in BGP this evening to manipulate traffic. In the instance below, I needed to give a lower preference to traffic that was learned from ‘65002’ and was 4 AS hops out. I did this by creating an as-path access-list, using it in a route-map, and applying it to an eBGP neighbor.

Google Chromecast and scanning for WiFi Networks

August 20, 2013 · Miscellaneous Hacking Google Wireshark

I’ve been playing around with the Google Chromecast this evening. One of the things that I’ve just run across is that it appears to periodically scan for wifi networks. I’ll write more soon, but this is what I’ve found so far.

Performing a full system restore after a Linux server re-kick

May 24, 2013 · Bash Tips Linux Backup and Recovery

Sometimes, a server becomes so corrupt that you need to re-install the operating system and perform a full system restore of the server from backups. After the OS re-install, but before you perform the restore, you need to create a backup of the files that are responsible for booting the server, defining the partition and file system layout, and naming the hardware. Once the full system restore has been completed, you should restore those files.

SDN Goodness

May 9, 2013 · Nicira SDN Openstack

Here are a few nuggets pertaining to OpenvSwtich, NVP, SDN, and Nicira.

Introduction to MPLS

May 9, 2013 · MPLS packetgeek.net

I ran across this (long) video. It’s a pretty good introduction to what MPLS is.

SELinux For Mere Mortals

April 15, 2013 · SELinux Linux packetgeek.net

I ran across a great video that discusses SELinux. It’s called “SELinux For Mere Mortals”.

Cisco Zone Based Firewall and UDP based Traceroute

April 11, 2013 · IOS IOS Security Cisco Firewalls

I’ve been using the Cisco Zone Based Firewall features in IOS for a little while now. Mostly at home and in a lab environment. One of the things that was kind of frustrating was that was the lack of outbound traceroute support from the trusted network to the untrusted network. I only use Linux and MacOS X at work and at home, so I never tried it out with a Microsoft based computer. I’ve also...

Filesystem I/O Speeds Benchmarking Perl Script

March 7, 2013 · Linux Filesystems Perl Tips

I wrote a quick perl script to test the read and write speeds of a file system in Linux. Below is the contents of the script.

Learning Python

February 28, 2013 · Python Tips packetgeek.net

I know and use Perl and Bash fairly regularly with automating system administration tasks. Lately, I’ve been putting some effort into learning python, as I believe that it will help me grow in my career. I’ve been using Learn Python the Hard Way. So far, it’s been a pretty awesome site! I need to think of some projects to continue to increase my capabilities with it. Maybe, I’ll post some code examples as I create...

Bash Shell Enumerator - Command Not Found

February 22, 2013 · Bash Tips Pranks packetgeek.net

Make this script run when ever a user logs into their system and watch them freak out as it tells them that all their commands aren’t found. :)

Bash - Random Password Changer

February 22, 2013 · Bash Tips Pranks packetgeek.net

Here’s a script that will change a user’s password at random internals with a randomly generated 30 character password. :)

Quick one-liner to change all databases tables to InnoDB in MySQL.

February 10, 2013 · Bash Tips System Administration MySQL

I’ve been attempting to get a better understanding of the operations of MySQL. For me, the best way to do that is hands on. I had a database, with a lot of tables, that I wanted to change the engine type to InnoDB. Obviously, being a lazy sys admin, I didn’t want to change them all by hand. So, I made a quick one-liner to do the job for me.

OpenNHRP RPM Updated

February 6, 2013 · OpenNHRP Open Source Alternatives packetgeek.net

I’ve updated the yum repository with the current version of OpenNHRP. The current version available in the repository is 0.14. For more information, check out the repository link. http://www.packetgeek.net/repository.

Linux File Server for Apple Time Machine Backups

February 4, 2013 · Linux netatalk afp

I got Apple Time Machine backups working with my Linux file server. Apple allows you to perform backups over the network utilizing the AFP (Apple Filing Protocol), via the Time Machine app. There is an open source implementation of afp in the netatalk package. Here is a quick and dirty run down of how I configured netatalk to work as my storage location for my apple backups.

Rackspace Private Cloud Edition - Compute Setup

January 19, 2013 · Openstack Private Cloud Edition Rackspace

I finally got a chance to sit down and play with pre-built Open Stack ‘Private Cloud Edition’ built by Rackspace. Once it’s installed, you can spin up instances right out of the box, but there are a few nuances to getting a functional platform for remote access and serving. I figured that I’d do a run through of the install and the initial changes that I made to get my install working.

Rackspace Cloud Servers and Networks with Open vSwitch and VXLAN between Data Centers

January 12, 2013 · Linux Software Defined Networking VXLAN

I’ve been playing with Open vSwitch and the VXLAN patch that is available at: https://github.com/mestery/ovs-vxlan

Playing with Openvswitch.

December 29, 2012 · Linux Software Defined Networking SDN

I’ve been playing with openvswitch a little bit this evening. Here are some notes that I took for a very basic configuration on Ubuntu 12.04.

The Nerdiest IPv6 related domain name on the Internet

November 2, 2012 · IPv6 packetgeek.net

I purchased a new domain last night. The site is 3.4028237e38.com. I don’t actually have any plans for it, yet. It will most likely just have a bunch of IPv6 related information on it. :) Check it out!

IPv6 Subnetting

October 30, 2012 · Subnetting IPv6 packetgeek.net

Subnetting IPv6 is just like IPv4, that is it uses the powers of two to determine the subnet mask. IPv6 doesn’t use a subnet mask, per say. Instead it uses slash notation. For example /64, /48, etc. The slash notation is known as a prefix.

SELinux - Listing Available Contexts

October 29, 2012 · SELinux Linux RHCE Study Notes

IPv4 Subnetting Made Easy

October 29, 2012 · Subnetting IPv4 CCNA Study Notes

RHCE Series: SSH and NTP

October 27, 2012 · Linux NTP RHCE Study Notes

RHCE Series: SMTP

October 27, 2012 · Linux RHCE Study Notes Sendmail

RHCE Series: HTTP

October 27, 2012 · Linux RHCE Study Notes Apache

RHCE Series: FTP

October 26, 2012 · vsftpd Linux RHCE Study Notes

RHCE Series: DNS

October 26, 2012 · Linux RHCE Study Notes DNS

Making NAT work with the default Red Hat iptables ruleset

October 26, 2012 · IPTables Linux Firewall

Just a mental note.

RHCE Series: Configure the service to start when the system is booted.

October 25, 2012 · Linux RHCE Study Notes packetgeek.net

RHCE Series: Configure SELinux to support the service.

October 25, 2012 · SELinux Linux RHCE Study Notes

Free Web-Based F5 Training

October 25, 2012 · F5 training packetgeek.net

F5 offers a free web-based course! How cool is that?

RHCE Series: Remote Logging

October 24, 2012 · Linux RHCE Study Notes Logging

RHCE Series: Produce and deliver reports on system utilization

October 24, 2012 · Linux RHCE Study Notes System Administration

RHCE Series: Build a simple RPM that packages a single file.

October 24, 2012 · Linux RHCE Study Notes OpenNHRP

RHCSA Class Notes

October 16, 2012 · LUKS RHCSA Study Notes SELinux

RHCE Series: Use /proc/sys and sysctl to modify and set kernel runtime parameters.

October 16, 2012 · Kernel Tuning Linux RHCE Study Notes

RHCE Series: Configure a system as an iSCSI initiator that persistently mounts an iSCSI target.

October 16, 2012 · Linux RHCE Study Notes ISCSI

RHCE Series: Use iptables to implement packet filtering and configure network address translation (NAT): Part 2

October 15, 2012 · IPTables Linux RHCE Study Notes

Think that you have a compromised Red Hat based system?

October 12, 2012 · Linux Security RPM

Use RPM to search for modified binaries.

RHCE Series: Use iptables to implement packet filtering and configure network address translation (NAT): Part 1

October 12, 2012 · IPTables Linux RHCE Study Notes

Making a VM boot at VM host boot in KVM

October 12, 2012 · Linux Virtualization KVM

PPTP to HE IPv6 Network Perl Script

October 11, 2012 · Linux IPv6 Perl Tips

I forgot about this. This was a perl script that I used to use to connect to Hurricane Electric IPv6 Network via PPTP. Last I checked, their pptp servers were offline. Bummer for those who can’t do IPv6 in IP tunneling. Requires the pptp-setup package.

RHCE Series: Route IP traffic and create static routes

October 10, 2012 · Linux RHCE Study Notes Routing Protocols

IPv6 Subnetting

October 9, 2012 · Subnetting IPv6 packetgeek.net

In conjunction with my knowledge of how IPv4 subnetting works, Ethereal Mind blog on “/48 allocation in /64 chunks” got my mind going on IPv6 subnetting and how it works. I’ll write more on it soon, but it’s pretty easy to understand if you understand how to subnet IPv4 networks. Same concepts, but with 16 bit fields and 128 bit long addresses.

RHCE Exam Objectives

October 7, 2012 · RHCE Study Notes packetgeek.net

OpenNHRP is now available via RPM

October 2, 2012 · Linux DMVPN System Administration

After a LONG hiatus, I’m finally starting to work on my Open Source implementation of DMVPN, again. So far, I’ve started off by taking the OpenNHRP source code and building RPM files. I made no changes to the source code itself. Heck, I don’t even consider myself a developer. I just built the RPM binaries so that a person could build a DMVPN device without needing to have developer tools installed on the device itself....

Using a Proxy Server to access the IPv6 Internet?

October 1, 2012 · Linux System Administration Proxy

I had an idea recently. Could a person use an http proxy server to access the IPv6 portions of the Internet? The answer is, yes.

Logical Volume Management in Linux

October 1, 2012 · Linux Filesystems System Administration

LVM is a very powerful file system administration tool in Linux. It provides you with the ability to create, extend, resize, and even take snapshots of disk space on live systems. Here are my notes. I created a new hard drive within my test VM. When the server booted, it sees the new drive as /dev/sda. The disk that’s in use by Linux is /dev/vda. To start, we’ll need to partition /dev/sda. Note that you...

Linux Encrypted Filesystems

September 30, 2012 · Linux Filesystems Security

In the age of mobile devices that contain private information, whether it’s personal or business information, encrypting your devices is a good idea. Filesystem encryption allows you to encrypt a single partition or even an entire hard drive. When configuring correctly, this will help mitigate privacy issues from stolen devices.

ASA Security Contexts

October 11, 2011 · Security Cisco Firewalls packetgeek.net

ASA Security Contexts

Cisco Auto Secure

October 10, 2011 · IOS Security IOS Security

I recently found a new command to help with the securing of Cisco Routers. The command is “auto secure”, which is executed from privileged enable mode. When executed, it asks a few questions and executes several commands based on security best practices for Cisco Routers. Below is an example from a router in my test lab.

IOS Local Password Security Features

February 17, 2011 · IOS Security IOS Security

I’ve been studying some of the security features built in to IOS. These mostly have to do with physical security and local password security built into IOS.

Backdoor in the openBSD IPSEC Stack?

December 15, 2010 · IPSEC Online Privacy packetgeek.net

Allegations regarding OpenBSD IPSEC

It's been a while...

December 2, 2010 · Misc. packetgeek.net

It’s been a while since I’ve updated this. I’ve since earned a CCNP and have several notes and such that I need to put up here from my studies. I’m also focusing on my professional development and continuing to learn more about advanced technologies in depth.

Layer 3 LAN Switching

August 8, 2010 · LAN Switching CCNP Study Notes Layer 3 Switching

LAN Switching Layer 3 Redundancy Protocols

August 8, 2010 · GLBP High Availability LAN Switching

Virtual LAN's and Trunks

August 4, 2010 · LAN Switching VLAN CCNA Study Notes

Diebold FIT File Perl Script

July 28, 2010 · Diebold Perl Tips packetgeek.net

I wrote this to generate Diebold FIT files quickly. This script can generate a FIT file in a couple seconds in what would take me hours to do by hand.

VLAN Trunking Protocol

July 27, 2010 · LAN Switching CCNA Study Notes CCNP Study Notes

OSPF Notes and Gotchas

July 20, 2010 · Routing Protocols OSPF IGP's

Open Shortest Path First (OSPF) is an open standard routing protocol that is used as an interior gateway routing protocol (IGP). Because OSPF is an open standard, it will inter-operate with many network gear vendors, with some configuration tweaks.

What information is your browser giving away?

May 18, 2010 · Perl Tips Online Privacy packetgeek.net

This morning, there was an article where the EFF is claiming that just because you turn off cookies and javascript in your browser doesn’t mean that you’re not giving away information. Unfortunately, they are very correct. Your browser will give away ALL kinds of information about your computer; such as operating system, browser type / version number, browser plugin’s, etc.

Automated Linux Backups utilizing rsync over SSH

May 16, 2010 · Linux System Administration Perl Tips

I was recently tasked with coming up with a backup solution for our Linux based servers. My solution was to use rsync over SSH to pull the data that we wanted over and then use tar to create daily archives, which we can then pull off the server to some other type of storage media or a remote server.

Virtualization Notes, Best Practices, and Gotcha's

March 21, 2010 · Virtualization Hyper-V VMware

I spent last week attending the Virtualization Pro Summit. I came away with a wealth of information that I’m still compiling, wrapping my head around, and figuring out where and how I can implement what. Below are some of the notes that I took away from the conference.

OSI and TCP/IP Layer Models

June 4, 2009 · OSI Model TCP/IP Model CCNA Study Notes

📚 Archived Content: This post is part of my historical study notes archive from 2009. While the fundamental concepts remain relevant, some specifics may be outdated. For current technical content, visit the Technology section.

NSA Security Configuration Guides

June 3, 2009 · Security packetgeek.net

I refer to these guides from time to time, but always end up doing a google search to find them. I’m not very good at browser bookmark up keep and I’m always on a different computer then the needed bookmark is on. :)

Using Perl to grab a proccess id in Linux

May 31, 2009 · Perl Tips packetgeek.net

Ever since I first started doing Linux system administration, I’ve used perl scripts to automate some basic tasks. I’ve never really been that great at writing scripts because I never took the time to sit down and really learn the intricate details of the language. Here recently, I’ve written some of my most complex and detail oriented scripts, where I’ve had to really learn a little bit about regular expressions. Along the way I also...

Prepping Ubuntu Server Edition to run as a DMVPN.

May 31, 2009 · Ubuntu SE VPN Perl Tips

After reading about the open source implementation of NHRP, I decided that I would play around with it a bit to see where it’s at, development wise. I have a VMWare Session of Ubuntu 9.04 (Server Edition) that I use to geek out on stuff like this. It’s nice, because at a click of a button I can have a default install, by reverting to my default snap shot.

An Open Source Implementation of Cisco's Dynamic Multipoint VPN (DMVPN)

May 31, 2009 · VPN Open Source Alternatives packetgeek.net

For a few years, Cisco has had a pretty innovative VPN solution called “Dynamic Multipoint VPN”. In essence, it’s a traditional hub and spoke VPN design, except that when two, or more, spokes want to communicate directly with each other, they initiate a dynamic IPSEC tunnel with each other instead of sending the traffic to the hub, where the hub would route the traffic to the destination spoke. If you’re confused, the “hub” would be...

A Net::Telnet::Cisco Example (Save Running Configuration)

May 31, 2009 · Cisco Administration Perl Scripting Perl Tips packetgeek.net

This is a simple perl script that uses the Net::Telnet::Cisco perl module to save the running configuration on a Cisco IOS router or switch. It could be modified to be automated very easily.