CCENT Exam Prep

This has been a long time in the works, but I just made a great break through.

I started cobbling together a study lab in the engineering lab room here at work. It is fairly well isolated from the rest of the world. A sandbox, if you will. Well, this particular lab happens to be poorly maintained by the engineering team and I find that I spend more time in there than anyone. I also am the guy who does the cabling in this building. Two things drove me over the edge. Well, three. Let’s call it a perfect storm.

1) The lab is wicked cold. I can’t be in there more than 20 minutes before I am uncomfortable.
2) It has no Internet access.
3) I want to work from my desk.

I have not found any kind of standard CCENT lab setup, so I just gathered up a few old/spare parts and built my own. There happens to be a Cisco access switch (terminal server) in the room with all of one connection to it, so I added my devices and have been happily playing around with getting into enable mode and loading new IOS code, etc, etc. BTW, booting your router from a TFTP server is pretty cool to watch. Anyway, this TFTP server thing is what started me thinking. If I wanted to work from my desk, but I needed a TFTP server running in the lab, but I needed Internet access to download the new IOS codes, what the heck was a boy to do!?!??! How about run a connection from my lab network to my desk on the far side of the building? Blam-O! Done! Copper to fiber to the data center to the nearest LAN closet to copper at my desk. Now I have my personal laptop attached to a switch on the far side of the building. But I still did not have Internet access and I had recently un-jailbroken my iPhone, which means no more tethering…which Verizon was really starting to bite my ass about (another story for another day). I had been moving the files between my werk lappy and my personal lappy via a USB thumb drive, but this was kind of a pain. Getting Internet accessibility to the lab was a must. And a dedicated server would be nice, too. Cisco Certified Entry-level Network Technician, indeed. 😉

So, again, what’s a boy to do? I realized that I had a WiFi card in this lappy that was doing nothing, so I turned it on and had a look around for any open hot spots. There was one Linksys showing, but it was too far away to connect. But, right outside my cube-farm window is a coffee shop with a wireless network running with WEP. I’ve read over the years about how easy it is to crack WEP, so I started looking into this and quickly found that my WiFi card is not able to do it…in Windows. But it was able in Linux. Soon after that, I discovered BackTrack Linux and installed it on a bootable USB thumb drive. {edit: BackTrack has since become Kali Linux.} The first couple of attempts did not go so well, but the next day I was successful. Turns out the WEP key is simply the coffee shop’s telephone number! Anyway, I was in and started looking around and found that it was a reasonably safe place to be. I’ve been using it ever since…and the speed has returned to my iPhone! Shocker.

Now I had access to the lab network and access to the Internet from the same machine at my desk. How to bridge the two? Internet Connection Sharing, of course! BAM! I was up and running — but only on the attached network, I could not connect from the routed network. Bugger and bother. I’ve spent the better part of two weeks wrestling with this issue. But first, the server.

I started off thinking that Debian would be the way to go, but without Internet access right off the bat, this proved difficult. The optical drive in the server box is CD-ROM only and, etc, etc, etc, poorly written partition manager, etc, etc, etc. It wouldn’t fly. I then tried Ubuntu, but the CD I was using has seen better days and the install failed right after starting to screw with the partitions. This box also has Windows Server 2000 (!!!) on it that one of the engineers sometimes uses when testing the wireless install. As such, I COULD NOT DESTROY the Windows Server install. I reburned Ubuntu and finished the install, but, you know what? I HATE Ubuntu servers.

So I fell back on what I knew and grabbed Fedora 17, which installed without a hitch. Some things have changed a bit in Fedora, but not so much that I couldn’t find my way around. This was great while working with it on the “external” subnet (, but it could not do a damn thing once I moved it to its permanent home on the “internal” network ( Two weeks.

I have been up one side of a static route and down the other side of a NAT. I have been reading every web site that ever mentioned Windows ICS…and a few that are about Android Ice Cream Sandwich. I even broke down at the end of the day yesterday and asked one of the engineers if he could spare a few minutes doing a deeper dive on NAT routing than the average bloke would ever need to know about it. I even discussed, this morning, what I was trying to do with my junior team member, who recently passed his CCNA and is on his way to the CCNP…so he, technically, outranks me. Even he didn’t know what was up, but he was entirely floored at what I had built out of spare parts and spit. He’s not a geek. 😉 Watching a Wireshark session running on the laptop, it struck me that if I can’t get this working in Linux, I should try getting it to work in Windows and then reverse engineering it in Linux. I broke out my troubleshooting FastEthernet hub (yes, hub) and a spare laptop that I have taken ownership of and set about making this sucker work at my desk on the “external” network. Once I saw the results, I packed the laptop up and went into the lab. I recreated the situation there and had the same positive results: Internet access in the lab from a connection running all the way to the other side of the building, through my laptop, out its WiFi adapter to the coffee shop across the street’s WiFi router and out their DSL modem. Yup, DSL. I then moved the laptop to the “internal” network and watched it not connect. It wasn’t a DNS issue, as I was able to resolve web addresses…I just could not get to them. I then started ripping out all the static routes and NAT statements and etc that I had been adding over the past two weeks and then it struck me, like a flash from above.

ip route

BAM! The laptop was immediately online from the internal network. I checked the server and found the same. I am so very happy.

Now I can go back to studying how routing works. Labs are great!

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