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Networking

extend dlink 655 wireless network with linksys (DD-WRT) and engenius routers: Part 1

by Ben
written by Ben

Introduction

Extending a wireless network is not an easy task.

There are various way to extend your wireless network – you can connect a cable directly from one router to another and extend from there OR you can ‘join’ 2 wireless router via wireless means.The article here will talk about the second option. The correct term for this wireless-wireless setup is Wireless Distribution System (WDS).

WDS

By definition, a Wireless Distribution System (WDS) is a system that enables the wireless interconnection of access points in a wireless network.
It allows a wireless network to be expanded using multiple access points without the need for a wired backbone to link them, as is traditionally required.

Limitation (or Requirement) of WDS

  • Some router might not support the newer WPA2 security. Note that Tomato firmware on Linksys WRT54g does not support WPA2 in WDS mode. Fortunately, DD-WRT does support.
  • Speed may decrease by 50%
  • Not all routers support WDS. I bought a Belkin N router and only realized that it doesnt support WDS wireless. Thus, do some ‘googling’ before you go and buy a wireless router.
  • A lot of patience for trial and error- if it doesn’t connect for the first time, try rebooting all the routers and try again.

My Wireless Setup

My setup is quite a challenging one as I am not only extending 1 router but 2.
Due to the location of my furniture in my living room, I have to extend 2 routers to cater for both my xbox360 and my wired network printer.

In short, my overall wireless layout is as below.

The routers that I am using for my setup are

Some basic concept/setup for WDS to work

  1. You need to manually set the ip address for each of the access points (sub-router) and the IP address must not conflict with each other. i.e. my dlink ip address is 192.168.0.1, and the rest of the router is 192.168.0.2,192.168.0.3
  2. The access point’s gateway IP should point to the main router. i.e. in my Linksys router, my IP address is 192.168.0.3 and the gateway IP is 192.168.0.1
  3. If you are using DHCP, you can set it in the main router ONLY or in each router. If you are using the latter option, the DHCP range must not conflict with the rest.
    For example, if you using only the main router for DHCP only. The main router DHCP ip address is set from 192.168.0.100 to 192.168.0.199
    if you are using DHCP for each routher, you can set 192.168.0.100 to 192.168.0.150 for router A, 192.168.0.151 to 192.168.0.199 for router B and so on
  4. Set DNS server in the access point  to your main router i.e. 192.168.0.1
  5. Wirerless SSID for all routers should be the same

My setup

  • Main router IP address is 192.168.0.1
  • Engenius router is 192.168.0.2
  • Linksys is 192.168.03
  • Subnet mask for all routers is 255.255.255.0
  • Using WPA2 AES security
  • Gateway IP and DNS are my main router IP address – 192.168.0.1
  • Wireless channel 6
  • Same wireless SSID for all 3 routers

Coming soon: WDS setup part 2

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Operating System

Solve TF2 ping spikes or onboard sound related issues in Windows 7

by Ben
written by Ben

omg, I had this ongoing “lag” issue in TF2 whereby my fps would drop dramatically in a fight in TF2 (team fortress 2) game.

Things get more frustrated when I recently upgrade my graphic card from the old 8600GT to the GTX260 and the lag problem does not go away!

Its only recently that I came across this thread in steam forum that suggest a fix to this problem.

if you have a similar setup like mine

  • Intel Core2Duo E6320
  • 4GB RAM
  • Windows 7 Home
  • GTX260
  • Onboard Realtek soundcard
  • MSI P65 Neo2 motherboard

and encounter the following symptoms…

  • lag or shutter after 2-3 seconds when you walk in a straight line in the game
  • framerate drop to 10+ in heavy fight
  • sound shutter in heavy fight
  • ping spikes randomly

for the following steam games…

  • Source Engine Games (Team Fortress 2 (TF2), Left 4 Dead, Counter Strike Source (CS:S, CSS))
  • Heroes of Newerth (HoN)
  • Call of Duty Series (CoD), possibly including Modern Warfare
  • Overlord Series (Overlord, Overlord: Raising Hell, Overlord 2)

perhaps you may want to try the following method and see if the problem would go away.

  1. Open regedit
  2. Go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile
  3. There will be an entry for network performance throttling, default value is 10; set it to FFFFFFFF hex (willl look like 0xFFFFFFFF to the right of the entry
  4. Reboot
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Operating System

Premature end of script headers in perl script

by Ben
written by Ben

‘Premature end of scrip headers’ error message refers to the script being stopped for whatever reason before it actually return any output to the browser.

The first time to check is to ensure the below codes are output first

print "Content-type: text/html\n\n";

And then to debug the error, simply add the below line(preferably after the above code).

use CGI::Carp qw(fatalsToBrowser);
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Codingjava

Create new log file with log4j FileAppender when using Quartz Scheduler

by Ben
written by Ben

Recently came across a problem whereby the quartz scheduler could not recreate a new log4j FileAppender log when the job is call again.

Googled a bit and found out a couple of solutions such as using a custom log4j classes, which create a seperate thread when being called in quartz scheduler.

I find that it is too complex and had try several ways to recreate the log file inside Quartz.

And finally came up with this one line of code.

Before I begin, let’s take a look at my log4j config.
This log4j config will create a simple console system out logger and also a FileAppender logger.
For my case, I want to re-create a new log file whenever this job is run.

log4j.rootLogger=INFO, stdout
log4j.additivity.stdout=false
log4j.additivity.joblog=false
log4j.appender.ROOT.layout.ConversionPattern=[%d] %t %c %-5p - %m%n

#console
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d %p - %m%n

#per job execution log
log4j.logger.com.yourcompany=INFO, joblog
log4j.appender.joblog=org.apache.log4j.FileAppender 
log4j.appender.joblog.layout=org.apache.log4j.PatternLayout
log4j.appender.joblog.File=../jobtemp.log
log4j.appender.joblog.Append=false
log4j.appender.joblog.layout.ConversionPattern=%d %p - %m%n

and here’s the schedule job

public class ScheduleJob implements StatefulJob {
	
	private static Logger logger = Logger.getLogger(ScheduleJob.class);

	public void startJob() throws SchedulerException{
		Scheduler scheduler =
			StdSchedulerFactory.getDefaultScheduler();
		scheduler.start();
	}
    
	public void execute(JobExecutionContext context) 
		throws JobExecutionException {
		
		//reset log4j config for FileAppender
		PropertyConfigurator.configure("../conf/log4j.properties");
		
		RunJobImmediately newJob  = new RunJobImmediately();
		newJob.performJob();
		
	}
	
	public static void main(String args[]){
    	try{
    		ScheduleJob scheduleJob = new ScheduleJob();
    		scheduleJob.startJob();
    		
		}catch(Exception e){
			logger.error(e);
		}    
	}
}

and finally the one line of code to recreate the log file.
Apparently, this line will somehow ‘reload’ the log4j  utitlies, which thus recreate the FileAppender logger to re-create the log file.

PropertyConfigurator.configure("../conf/log4j.properties");

Feel free to let me know if there is any performance issues or it is not working at your side.

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