subtafuge.com Just some stuff on the web

28Apr/130

Bridged WiFi routers via LAN/Homeplug?

wifi-logo

This will be a quick post about a problem I was having. I have two Wireless N routers, and have them connected via LAN (through a Homeplug) so that I could extend the WiFi through my property.

This was working fine for most of my devices but I have been having problems with my Windows 7 netbook (Samsung N140): When I was in range of the second router I would be connected to the WiFi with a strong signal, but the internet would be intermittent. Highly frustrating.

After a load of troubleshooting, and changing of firmwares, I finally figured out the problem....and it is a silly problem.

First, my configuration: I have a TP-Link 1043ND router, which I managed to brick. I then bought an ASUS RT-N16 to replace it. I put TomatoUSB on this router and it works like a dream...it is a fantastic router with a great spec. It was however bugging me that my TP-Link router was bricked so I pulled it apart and soldered a USB to TTL cable to the board and followed these instructions. After a few attempts I finally managed to unbrick it.

Now that I had a second Wireless N router, I put this in the opposite end of the house to my main router, and connected it via Homeplug (effectively a LAN cable). If you haven't actually got to this stage yet, the setup is pretty simple:

How to bridge two routers via LAN to extend your WiFi

  • Make sure only your first router is set up as a DHCP provider, disable this on the second router
  • Set DHCP to provide a range of IP's from x.x.x.100 - x.x.x.200 (i.e. 192.168.0.100 - 192.168.0.200).
  • If your main router is set to IP of 192.168.0.1 then set the second router to a static IP on the same subnet...i.e. 192.168.0.2, and make sure the IP is lower than the DHCP IP range set previously (less than 192.168.0.100).
  • When connecting the main router to the second router, don't use the WAN port. Plug the routers together using one of the LAN ports on each.
  • Set the SSID (WiFi Name) to the same name on both routers, also make sure the security settings are the same...i.e. WPA2 PSK/AES on both, AND make sure the password is the same too.
  • The last thing to do is set the channels for the WiFi to manual, and make sure they are different. Try get them on opposite ends of the spectrum. i.e. for my setup I have one router set to channel 1 and the second to channel 11.

You should effectively have seamless WiFi on your property now. Moving between the areas of the two routers should switch the signal to the strongest signal seamlessly.

This is where I got stuck. The instructions above are pretty much the instructions you see anywhere else on the web, and they work for the most part. My Android devices don't have a problem with this setup and neither do the wireless cameras I have. But my netbook kept having intermittent internet issues.

The simple fix? Make sure your channel width in your WiFi settings are the same on both routers! Wireless N allows you to choose between 20MHz or 40MHz. 40MHz theoretically provides more bandwidth (150Mbps vs 54Mbps), but 20MHz provides backwards compatibility for older devices. I don't have any problems on 40MHz, but if you do, then switch both routers to 20MHz.

Below is an example of the setup on my main router (running the brilliant Toastmans' version of TomatoUSB)

TomatoUSB WiFi config

and below is a screenshot of my TP-Link 1043ND router setup (I had it runing on DD-WRT, then on Gargoyle...but reverted to the stock firmware as the WiFi performance appears better with it):

TPLink 1043ND WiFi config

Let me know in the comments if you are having any further issues with your bridged router setup.

23Jun/1212

Intelligent bruteforce password attack for Excel, for free

Sometimes there is a need to open an Excel file that you don't have the password for. Occasionally this will be when a colleague who has password protected an Excel document has now left the company...usually it is because the idiot who password protected the document forgot the password.

I work in the IT world, and this problem comes up on a pretty frequent basis...even more so because I am involved in the security and investigations realm. Usually when I need to get into the document I would use a brute force method. Unfortunately even with the best commercial solutions, brute force can take a ridiculous amount of time...and for the average person these solutions are not cheap. For excel files that were made in versions of Excel earlier than Excel 2007, this method will still work, but isn't entirely necessary. Excel 2003 and earlier is a lot easier to crack than later versions. From 2007 onwards, there is a level of encryption involved. Also, this method is for the password used to open the Excel document, not the password protected sheets and formulas (these are simple to bypass anyway).

If you aren't sure what brute force is, basically it is checking every possible combination of passwords possible. Starting from A to ZZZZZZZZZZZZZZZZZZZ. This is a pretty quick process if the password is 3 or 4 characters long and doesn't include special characters (!,*,% etc). Start looking at 7 character passwords and it is near impossible to get the password using this method unless you have quite a bit of cash to spend. Check this link to see how long a typical bruteforce attack would take.

6Feb/110

Facebook: Download your entire history!

Try this out:

  1. Log in to your Facebook account.
  2. Click on Account
  3. Click on Account Settings
  4. Click on "Learn More" next to "Download your information"
  5. Click on the "Download" button

You will receive an email with a link to a ZIP file which contains all the information you have put on Facebook: every link, every status update, every picture since you started on Facebook.

I guess this is quite handy. But it is also rather scary how easy it is to create a profile about you in such an easy way.

Warning: You will very likely cringe at some of the stuff you have posted since starting on facebook!

21Nov/090

Google Chrome OS: New Kid on the Block

It was inevitable that Google would enter the Operating Systems market (although you could say they already have with Google Android). True to form, Google have introduced something that defies convention. They have introduced an Operating System that promises to be all about "speed, security and simplicity".

29Aug/090

JAVA Speech Recognition

I was messing around today with speech recognition. It seemed like it was going to be pretty easy, and it was...except for the first step: Getting hold of the API!

Here is the JAR file : jsapi.jar
Import this into your IDE (typically into the "library"), then add the following lines to your code:

import javax.speech.*;
import javax.speech.recognition.*;

Below is a link to get you started with using it, enjoy!

http://java.sun.com/products/java-media/speech/forDevelopers/jsapi-guide/Recognition.html

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