I shared my cable connection(ISP is AT&T broadband) to 3 computers with a gateway. It worked fine for the last 8~9 months, and I also have a website set up on one of the computer. Two days ago, I got difficulties receiving emails and people were not able to view my website.
I tried to figure out what's wrong, and here are what I found:(Cable modem is Motorola Surfboard SB4100 and gateway is Dlink DI-713P)
1.From the log on the gateway, there's a "Connection is broken" message every couple minutes. Then the gateway re-request IP from cable modem, and lost connection again. The loop kept going. The other thing I found is that the first lease of IP had 96 hours in the lease length, but the rest of them had only 1 hour.
2.Then I power-cycled the cable modem, reset the gateway and upgrade the firmware(of gateway) to latest version. Still the same problem.
3.I directly connected one of my computer to cable modem, everything looks fine, and the lease length is 96 hours.
4.I used an old gateway(Dlink DI-604,which was replaced just because I want wireless connection) and the log messages were the same.
5.I called AT&T, they said from their side the cable modem looked fine(signal strength or something...)
I can't decide which one is the problem. Please let me know what you think. Any comment is appreciated.