internet network goes out, but cable modem and router seem to be working

Have a question or want to start a discussion? Post it! No Registration Necessary.  Now with pictures!

Threaded View

I am having trouble with my internet connection.  I have a Motorola
SB4200 and a Dlink DI524 wireless router.  The cable modem shows
connected and locked with activity lights and the router is blinking
network activity as it should.  But the internet connection is lost as
much as once an hour, or sometimes less than one time a day with no
pattern.  Powering off the modem and router then restarting always
solves the problem for a while.  I noticed in my cable modem log file
that I keep getting the following message "5-Warning D520.2 DHCP
Attempt# 1 BkOff: 4s Tot DSC:1 OFF:1 REQ:1 ACK:1"  I seem to get it
when the internet is dropped.  The modem has DHCP enabled with an IP
range of and the router also has DHCP enabled with a
IP range of The router shows the home network
computers to have an IP address assigned by the router and not the
cable modem.  Do I need both the cable modem and router to have DHCP
enabled.  I could find no way to disable the DHCP on the cable modem.
And, is the warning message in the Cable modem log indicating why I
keep losing my internet?  The wife is not happy about all the problems.
 So any help would be appreciated.  This all seemed to happen when a
thunderstorm caused my old linksys wireless router to have 3 of the
switch ports fried and one of my computer's NIC card.  I can
communicate with the router and modem when the internet is working
using IE.  When it isn't working, I can get to the router's setup, but
not the cable modem.  I suspect the cable modem is tired and needs to
be replaced.  Let me know what you think.  Attached is the cable modem
log file.

Thanks Tom

Re: internet network goes out, but cable modem and router seem to be working wrote:
Quoted text here. Click to load it

Your attached file won't appear for most people as this is not a binary
group. Some folks won't even see your message minus the attachment. But it
doesn't matter.

Your computers will get their IP addresses from the DHCP server in your
router. Your router gets it's WAN IP address from the cable network. And
your cablemodem also gets an IP address from the cable network for the cable
network. (This is not the same IP address as the webserver in the cablemodem
that you use to view it's status page.)

What seems to be happening is when you are power-cycling the cablemodem the
modem is getting a short lease. A very short lease. And when it tries to
renew the lease, it is unable to do so.

There are a couple of reasons I can think of why this would happen. One is
that there is work going on in your area, and they want to make sure the
modem checks for a new lease frequently. But then we have the question of
why it can get one when you power-cycle it, but not in the normal course of

Another possibility is that the first lease you are getting when you
power-cycle the modem is a temporary lease that allows brief connectivity
for any modem put on the network. When that lease expires, a new lease needs
to be issued by the regular DHCP server, which isn't issuing your modem a

If there was a DHCP server problem, everyone in your region would be
suffering the same fate. DHCP server failures can't go on for very long
without causing major problems for the network, so we can probably rule out
a server problem.

What that leaves, in no particular order, would be a problem with your
account, a problem with your modem, or, if the problem isn't as consistent
as it seems in your post, a line problem. Normally I'd say an account
problem would be more likely, but since you mention a recent lightning
strike, I'd move the modem to the top of the list of possible causes.

Warren H.

Disclaimer: My views reflect those of myself, and not my
employer, my friends, nor (as she often tells me) my wife.
Any resemblance to the views of anybody living or dead is
coincidental. No animals were hurt in the writing of this
response -- unless you count my dog who desperately wants
to go outside now.
  Have an outdoor project? Get a Black & Decker power tool:: /

Re: internet network goes out, but cable modem and router seem to be working

Quoted text here. Click to load it
When you got the new modem, did you notify the provider?  Perhaps they did
not provision the new modem properly, thus preventing it from renewing it's
IP lease.


Site Timeline