If you are experiencing frequent disconnections (frequent means more than once per day) with your D-Link DSL-500 or DSL-504 router, there are several possible causes.
If you are running any Peer-2-Peer/file sharing software applications, the disconnections are very likely to be being caused by your software application creating new TCP/UDP connections faster than your router is expiring the old ones.
You can upset most, if not all, SOHO or consumer grade routers using P2P applications like BitTorrent if you are creating TCP/UDP connections faster than they are expiring. Eventually the router simply runs out of memory and then exhibits undefined behaviour which includes "crashing", "locking-up", disconnecting the ppp session or even losing line sync in some cases.
This has been more a complaint with routers other than the D-Link DSL-50X series since D-Link provided the ability to reduce the "life" of TCP and UDP connections with the release of its v2.21.x series firmware in late 2002 which allowed the end user to configure the default life of these connections.
In the web interface, go to Configuration -> IP Masquerade Timer and set the TCP timeout value to 5 minutes (down from the default 15 minutes) and the UDP timeout value to 1 minute (down from the default 5 minutes), press "OK" and then choose "Save changes and reboot system now" to be sure, to be sure :) Enjoy your new-found reliable connections.
A side effect of shortening the life of TCP connections is that applications like Telnet and SSH and protocols like NNTP which may remain idle for long periods of time will be disconnected if they remain idle for longer than the TCP life which you set. This would not normally be a problem for people who are using P2P or other file sharing applications as your Telnet/SSH/NNTP performance would generally be shocking anyway :)
If you are not running any Peer-2-Peer or file sharing software applications, but you notice a lot of ADSL activity (the ADSL Act LED flashes a lot) even when you are not using the Internet, then you may be suffering from one of a growing number of "worm" infections.
To diagnose this problem and fix it permanently you are going to have to acquire one of the leading anti-virus products on the market. If you already have one of these anti-virus products installed, make sure that it is still enabled (some worms have been known to disable your anti-virus software) and that you have up-to-date virus definitions. I personally swear by the Norton Anti-Virus software product, the 2003 version of which can be acquired [as at November 2003] as part of Norton's SytemWorks 2003 product from eBay for around $18-$25 including postage (RRP is ~$200, though the RRP for Anti-Virus by itself is ~$99).
Information about tracking down current worms may also be found on Symantec's website. Symantec also often provide free tools for removing specific current worms. However, I still recommend that you acquire your very own, legally licensed copy of Symantec's Norton Anti-Virus product.
An incorrect ADSL mode setting always results in a loss of line sync (ie the ADSL Link LED turns off).
For instructions on how to fix this problem, see Line dropping out? Configure the router in G.DMT mode. Note that if you are using G.DMT mode, you may need to switch to ANSI mode (no one can explain why, it just happens to work for a very, very small number of users).
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| Copyright © 2003, Trevor B Roydhouse |