Connection between Cable Modem and Gateway.

chihua00 used Ask the Experts™
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.
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if you aren't running wireless try replacing ethernet cables
Do I understand that you have a web site and a e-mail host behind a cable modem "Two days ago, I got difficulties receiving emails and people were not able to view my website"

Most likely, your cable provider changed your IP address.  How are you handling DNS on this??



Sorry I made the confusion.
1.I have a website set up on one computer, which is running linux, not hosting e-mail service nor receiving e-mail.
2.I had difficulties receiving e-mails on another computer, which is running Windows.
3.The IP address remained the same. The weird thing I noticed is the short lease time. It used to be 96 hours but now only 1 hour. AT&T customer service rep. said it should not be a problem though....
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I tried different cables but still the same.
Is the e-mail that you are not receiving POP3?  Do you require a static IP.

How can you possibly have a web site up with a dynamic IP address on a cable modem.  Are you using dynamic dns?

Can you, from your Windows PC, get to a www address.  What can you do and what can't you do.  Lets concentrate on the Windows machine because I don't have a clue with linux.  (I understand TCP/IP though).  Its probably not a problem with your system, or the cable, I think this sounds like DNS.



The 'connection is broken' message is from gateway's log, and it's there no matter my computers were on or not. Therefore I believe it's not system related.

For internet connection, I can connect without problem when the computer is directly connected to cable modem. When using the gateway, sometimes the connection is okay, sometimes not.

And for using dynamic IP to set up a website, there're some service provider that will match the domain name to the IP address you provide. The only annoying thing is you have to change the IP address you give to the service provider once the IP changes.
Yes, I know about dynamic DNS and others.  

Ok let me ask, where are you...  Are you in the US?

Are you sure that the Dlink has the latest firmware installed?

Do you have a 'Keep Alive' setting in the Dlink?



Yes, I am in Minnesota and I'm using AT&T's broadband service.

The D-Link gateway is installed with lastest firmware I can find from their official website.(Didn't really matter though since the error messages were the same before and after.)

I set the 'Renew IP forever' option in the gateway on so it will re-require IP when connection is broken.

Any thought about the lease time problem?
One of two things on the lease period.  a, your cable company has a problem, maybe they cant resolve your username and thats their workaround, or b, maybe your using some kind of setup username and password and not the right one.

Why don't you ask them for a new password....

Or, maybe they measure the uplink bandwidth your using and this is their way of controlling it.  DSL providers don't like servers.

what's ATT say.

Here's the thing, I've had this problem before.  I use to have it with Bell Atlantic at all my clients.  I was using a Linksys router and I resolved the problem everywhere by installing an upgraded firmware...


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