Help! I have a duplicate IP at a remote site!

Duplicate IPs on the same network are one of those things that are never supposed to happen but they never seem to go away. Usually, they are pretty much a non-event, someone can go shout at the user who assigned a static IP to their workstation on a DHCP subnet, the snapshot VM that was just spun up can be shut down, etc.

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What is Anycast?

Do you have multiple servers with the same content or purpose? Do you want every client to always take the best path to the closest one?

Anycast is for you!

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Issues Presented by Geographical DNS

DNS, the Domain Name System, has become something of a Swiss Army Knife of networking and systems engineering. One of the tools in this set determines a user’s location, and then send an IP address of a nearby server that can service the request.

On the surface, this seems like a great idea. Let us dig deeper and see what it can break.

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JMac's Learning Series

I get asked to explain networking concepts on a fairly regular basis. In-person, on slack, by e-mail, on LinkedIn, etc. I’m (almost) always happy to answer them, usually by drawing on any available surface.

That, though, is not the best way to let as many people as possible learn from my experience (read: mistakess) so I thought that this might be a better forum.

Have a question you want answered here? Hit me up on LinkedIn

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Github Pages - Moving Jekyll to Bootstrap4

Looking for more flexiblity in my layout for this website, which runs on GitHub Pages I started looking into adding Bootstrap for theming. I’d already changed most things pretty drastically, so there really wasn’t a lot to do.

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CCDE Written - First Try

Lots of people seem to do these blog posts, I think mostly to decompress after an exam. I definitely feel that need right now. In this post I’ll give the some of the thought process going in, as well as what prep I did (or did not as you might see) before taking the test.

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Some useful network scripts

Yeah, just realized I couldn’t find scripts on my computer and I didn’t remember what anything was named or what it did.

More Added Since, checkout my GitHub Gists

So, here are the first 2 I came across tonight:

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GitHub - Forking a repository you've already cloned

I find that most of the time, when I am forking a respository to do a pull request, I’ve already cloned the respository. I don’t do it often enough that I have it memorized, so I go looking for guides… and find that they all are for cloning a new repository, making changes, then doing the pull request. Then I go look up the actual commands that I want and proceed.

This is here for me, and, presumably, you to follow step by step those rare times that you need it.

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GPG Symmetric Encryption of Disk Image

I like to tinker with encryption, not because I have any real use-case for it, but because I find the entire subject enjoyable.

Just thought I’d take a moment to share with you the bit I was working on tonight: A symmetric (passphrase) encrypted disk image usable on Mac, Linux, and Windows.

WARNING: I am in no way responsible if you do something to break your data or your computer. Make sure passphrases you use are accurate and you can remember them, there is no way to recover an encrypted file without them.

First up: Create the disk image, I chose ExFAT as the filesystem as it is reasonably portable and standardized on as the filesystem for SDCards means out of the box support on most systems (including Raspberry Pi). I’m using .dmg as the file extension because Mac requires it on creation. Feel free to use whatever suits you.

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First Post!

This is definitely a first post.

JMacLabs.com has had a lot of first posts since it was first registered in 1995. Most of the content hasn’t followed it between iterations, and today none of the original content is left. The old sites were all static hand-typed html, then migrated to mostly html but with Perl CGI, photo galleries, etc. The first reference I see online is from 2002 and includes a link to the “old site (photos)” which includes stuff like this:
JMac At Jefferson Airport

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