The newer versions of the firmware for the Linksys routers supports the UPnP service that Microsoft included in Windows XP. What does this mean? Well, it means that every 30 seconds, the router sends out 10 packets saying "Hello, I support UPnP". This is sent out with a destination address of 184.108.40.206, which is multicast. This isn't really a security concern, more of a nuisance of seeing all these extra packets of traffic. So, if you wonder why the lights on router flashes every 30 seconds, there's your answer.
I received some interesting information regarding the port filtering feature on the Linksys router the other day. Someone send me a question regarding some error messages he received from the router, like "AT table full" and "checksum error". Also, he noted that with port filtering enabled, the router would be "pretty unhappy", and when port filtering was removed, the router was fine.
My own Linksys router also turned out to get unhappy, especially when I downloaded mp3's off of Usenet. The router would freeze up frequently, and I had to hit the reset button every perhaps a couple of times every evening to bring the router back. I did not experience this behavior when I first got the router, but not too long ago, probably after I added the 135-139 port filter, I did experience some instability in its behavior. Unfortunately, my Linksys router is no longer connected, so I cannot remove the filters to verify that it'll perform flawlessly after the filters have been removed, but I think there's been reported enough issues with the port filters to not recommend the use of port filters with the Linksys router. One person even added filters to block out every port with the exception of only a handful of standard ports. He's router didn't do too well at all.
So. If you're Linksys router keeps crashing, and you have port filters. Remove them and see if things improve.
Thanks to Scott Jordan for sharing his experiences with me.
© 1999-2005 Lars M. Hansen