DHCP

DHCP

DHCP is like Costco and Walt Disney.  Almost everyone has heard of it!  We all know that DHCP is the magic that dishes out IP addresses to our computers.  And we know that DHCP just works.  But how does it really work?

I’m all about the why.  When I was kid I bet I importuned my parents by inundating them with “Why’s”.

  • Me: “Dad, why is the sky blue?”
  • Dad: “Because that’s the way God made it.”
  • Me: “Why?”
  • Dad: “He has his own purposes”
  • Me: “Why?”
  • Dad: “Oh my gosh… stop already!”

hahah

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Posted in Linux, Mac OS X 10.10 Yosemite, Mac OS X 10.8 Mountain Lion, Mac OS X 10.9 Mavericks, Windows, Windows 10, Windows 7, Windows 8, Windows 8.1, Windows Vista, Windows XP Tagged with: ,

Networking 400: Secret TCP three-way handshakes

TCP secret three-way handshakes

So we all know that IP addresses allow us to communicate across the network by telling us source and destination layer 3 addresses.  But that’s just one bitty part of network communication.

If you’ve been following my blog you know IP addresses is the minutiae of network communication.  In fact, IP is nothing without TCP baby!  Let’s enter the secret world of TCP and its super exclusive handshake. Read more ›

Posted in Google Chrome, Internet Explorer 10, Internet Explorer 11, Internet Explorer 9, Linux, Mac OS X 10.10 Yosemite, Mac OS X 10.8 Mountain Lion, Mac OS X 10.9 Mavericks, Mozilla Firefox, Opera, Safari, Samsung Galaxy S4, Windows, Windows 10, Windows 7, Windows 8, Windows 8.1, Windows Vista, Windows XP Tagged with: , , ,

How to setup an 5520 ASA 5.2 in GNS 3 version 1.3

Image credit aliimg.com

Would it be nice if you could console into a virtual ASA 5520 running ASA 8.4.2?  You could setup NAT, site-to-site VPNs with virtual hosts and go crazy with firewall rules.  The answer is yes, you can and I’m about to show you how I did it on my Mac OS X 10.10 host using GNS3.

Here’s what I did to get this working…

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Posted in Hardware, Mac OS X 10.10 Yosemite, Mac OS X 10.8 Mountain Lion, Mac OS X 10.9 Mavericks, Windows, Windows 8, Windows 8.1 Tagged with: , ,

Wireshark 303: Finding malicious traffic on your network

Wireshark Advanced

Let’s say you and I went out to the local bar down the road and threw back a few beers.  We would get to know each other.  You would ask me what I do for a living, how’s the blog and if I had any brothers or sisters.  And I would ask you about your hobbies, whether you have a family and your role at your current company.

And let’s say during our little interaction I discover that you’re the Senior Network Engineer at a large financial firm in New York City.  You begin telling me how much you love your job, the benefits and salary.  And then I ask you the million dollar question…

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Posted in Linux, Mac OS X 10.10 Yosemite, Mac OS X 10.8 Mountain Lion, Mac OS X 10.9 Mavericks, Windows, Windows 10, Windows 7, Windows 8, Windows 8.1, Windows Vista, Windows XP Tagged with: , , , ,

Wireshark 301: Spying on what people are downloading (Part 2 of 2)

Wireshark Advanced

In the previous guide on spying on captured packets, I showed you to eavesdrop on the photos and movies people are downloading on the network.  In this guide we’re going to step it up a notch and only see the password a user entered but also decrypted an encrypted traffic stream.

Always make sure you have the authority to launch the attacks I’m going to show you. It’s not worth getting fired or embarrassed; ask before you hack.

And with that: let the bedlam begin!

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Posted in Linux, Mac OS X 10.10 Yosemite, Mac OS X 10.8 Mountain Lion, Mac OS X 10.9 Mavericks, Windows, Windows 10, Windows 7, Windows 8, Windows 8.1, Windows Vista, Windows XP Tagged with: , , , ,

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