Re: DHCP Not working

insanesquirle · ‎2017-09-20

My once fine-working cable modem has randomly stopped assigning IPV4 addresses to all of my devices. IPV6 is on auto-assign and works fine. I verified that IPV4 is set up for DHCP, but none of my devices are receiving an IPV4 address.

If I manually assign an IPV4 address to a device it works fine and I am able to access anything on the web. I've tried rebooting, and then factory resetting, still not working.

I used the netgear utility and my firmware is on its latest version.

Firmware version: V2.01.22

This is happening on wired and wireless devices.

Any ideas?

Bryansix · ‎2018-01-19

Same thing happened to me. I'm on an older Firmware of 2.01.14

I disabled DHCP, rebooted, enabled it, rebooted again and now it's working. We will see for how long.

antinode · ‎2018-01-19

> Re: DHCP Not working

   How do you know that the fundamental problem is DHCP, and not, say, a
totally broken connection? As usual, showing actual actions with their
actual results (error messages, LED indicators, ...) can be more helpful
than vague descriptions or interpretations. What observations, exactly,
led you to this "DHCP Not working" conclusion?

   Do the LED indicators on a wired connection (both ends) always look
good?

   If you have a computer with a suitable static IP address (so that it
doesn't need DHCP from the router), preferably wired, can you always

talk to the router's web site?

   Many things can leave a computer/device without a good IP
configuration. A bad DHCP server is only one of them.

> I disabled DHCP, rebooted, enabled it, rebooted again and now it's
> working.

   How much of all that necessary? Will a simple reboot do the job?

   Depending on how deep you want to dive, it may be possible to probe
the operation of the router at a lower level. There are various
programs out there which may be able to enable a Telnet (command-line)
interface to many Netgear routers. (I use the program which I modified,
http://antinode.info/nte , but others are available). Around here
(D7000, V1.0.1.54_1.0.1), for example, I can see if the DHCP server is
running:

# ps | grep -i dhcp
1152 root       704 S    /var/udhcpd_1 /etc/udhcpd.conf1
[...]

That doesn't prove that it's working, but if it died, then that would be
detectable and interesting.

Bryansix · ‎2018-01-20

The telnet thing is interesting. I'll have to check that out when I have time.

I rebooted the router at least 6 times. I tried both a hard power cycle by taking out the power cable and a soft reboot via the web interface. I had connectivity to the router via ethernet and wifi on my computer and neither were getting a DHCP address. ipconfig / release && ipconfig /renew did nothing. Only once I disabled DHCP, rebooted, enabled it, and rebooted again did it finally start assigning IP addresses again.

One thing to note is that the router seems to have lost its time as some point because some of the logs look like they are from 1970.

antinode · ‎2018-01-20

> One thing to note is that the router seems to have lost its time as
> some point because some of the logs look like they are from 1970.

   Hmmm. That sounds like a wholly other problem (can't contact
Netgear's NTP servers?).

   If this thing's little brain is sufficiently scrambled, then it may
be time to try the usual panacea: a full reset and (manual)
reconfiguration of the router. Or the super-panacea: reload the
firmware (and then apply the ordinary panacea).

> The telnet thing is interesting. [...]

   It might be educational to poke around, and try to see what's
happening before geting brutal. But even knowing that, say, the DHCP
server dies spontaneously may not actually tell you what to do about the
problem.

insanesquirle · ‎2018-01-20

My issue has been resolved. I called my ISP and had them push a firmware update through and the problem was resolved.

I knew it was a DHCP issue because with DHCP I was only getting an APIPA ip address but if I set a static IpV4 address I was able to communicate to the internet. I also knew because I had an IpV6 address through stateless auto-configuration which also could communicate to the internet. If it was a simple connection issue I wouldn't have been able to have successful communication through either of these protocols. The issue was most definately DHCP not assigning addresses.