RT-N66U can't pull DHCP from Comcast

[iefbr14]

I've tried two current firmware versions from the ASUS website, and one from Merlin, and still the router is unusable for Internet. PC (Win7) pull address just fine, and so does my very old Linksys WRT54GS.

Tried many reboots of modem (SB5120), tried cloning my laptop MAC after it was successfully connected, but nothing is working. Strange thing is that this router worked out of the box. It was not until I upgraded firmware to fix several issues that this major issue appeared.

I'm about ready to send it back to Amazon unless somebody knows of a fix/workaround.

 

[RogerSC]

Did you clear the nvram in your router after upgrading the firmware? When you upgrade firmware, if you have problems, the first troubleshooting step is to clear the nvram and then re-enter your settings manually.

There are several ways to clear the nvram on your router...there's a "Factory Default" button under "Administration" -> "Restore/Save/Upload Settings" in the web admin GUI. Or you can use the WPS button by holding it pushed in for a few seconds while powering on the router. Also, you can login via telnet and use the "mtd-erase -d nvram" command.

Hopefully this will help you.

 

[iefbr14]

RogerSC - Thanks for the reply. I had tried all of those except telnet, so for fun I tried that just now, but was unable to telnet in (or SSH, for that matter). Maybe because I'm back to the non-Merlin image.

 

[RMerlin]

Don't just reboot your modem - leave it powered off for 10 minutes. You need to give you ISP enough time for the current session to time out.

Also see the System log if there is any additional information.

 

[RogerSC]

RogerSC - Thanks for the reply. I had tried all of those except telnet, so for fun I tried that just now, but was unable to telnet in (or SSH, for that matter). Maybe because I'm back to the non-Merlin image.

Telnet needs to be enabled, it's generally off by default. To enable telnet, just go to "Administration" -> "System", and you'll find it there.

Good luck!

 

[supe]

I use Version 3.0.0.4.374.168 with comcast. the 200 series gave the same issues u describe when i last tried 2 of them. I haven't tried Rmirlin's versions lately but, his first 372 build was ok for the day I had it on.

As Rmerlin stated, u need to let comcast side time out for 10 min.

 

[iefbr14]

I had tried leaving the cable modem off for an extended period, but just to verify I left if off for 20 minutes just now (extra time was so I could go out to Ebay and buy a Cisco 2940 for 25 bucks, which will let me span ports and snif out what's really going on here).

Anyway, after 20 minutes I powered up from a Factory Default condition, and behavior stayed the same.

Also, as a note, I am indeed able to swap back and forth between Linksys and the PC with just a reboot of the cable modem. Bottom line is I cannot get connectivity to fail with direct PC or with Linksys and can swap back and forth as much as i like, with just one-minute reboots (and, no, MAC is not cloned); yet I cannot get connectivity to succeed with the ASUS.

And just for grins, when disconnecting the ASUS just now I re-connected the Linksys back WITHOUT powering off the cable modem. And it connected without needing the cable modem to be power-cycled. Which tells me that Comcast never learned the ASUS MAC.

One other thing that's indicating I just have a bad box - All along these days of troubleshooting I've seen - at least a dozen times - a MAC show up under "MAC Cloning" all on its own. Twice it's been the actual MAC of my laptop wired NIC; once it's been all zeros; and numerous times it's been random numbers (all valid MACs of some sort) that have nothing to do with any NICs on my PC or anywhere else that I know of. Very weird. I've cleared it out and saved, then a few minutes later a different MAC shows up. I did experiment with Cloning during my troubleshooting, but I always used the wired NIC of my PC. These random appearances I tossed up to buggy firmware, but it occurred in multiple versions of firmware.

I don't see a way to attach a file here, so here are a few log entries that seem related, if not relevant:

Jan 1 00:00:10 stop_nat_rules: apply the redirect_rules!
Jan 1 00:00:10 WAN Connection: ISP's DHCP did not function properly.
Jan 1 00:00:10 RT-N66U: start httpd
Jan 1 00:00:11 disk monitor: be idle
Jan 1 00:00:11 miniupnpd[331]: HTTP listening on port 54407
Jan 1 00:00:11 miniupnpd[331]: Listening for NAT-PMP traffic on port 5351
Jan 1 00:00:13 dnsmasq-dhcp[310]: Ignoring domain [###scrubbed] for DHCP host name [###scrubbed]
Jan 1 00:00:22 dnsmasq-dhcp[310]: Ignoring domain [###scrubbed] for DHCP host name [###scrubbed]
Jan 1 00:01:00 rc_service: httpd 311:notify_rc start_autodet
Jan 1 00:01:03 rc_service: autodet 348:notify_rc restart_wan
Jan 1 00:01:03 stop_wan(): perform DHCP release
Jan 1 00:01:04 rc_service: httpd 311:notify_rc start_autodet
Jan 1 00:01:04 rc_service: start_autodet is waitting restart_wan...
Jan 1 00:01:05 stop_wan(): perform DHCP release
Jan 1 00:01:09 rc_service: autodet 353:notify_rc restart_wan
Jan 1 00:01:09 stop_wan(): perform DHCP release
Jan 1 00:01:11 stop_wan(): perform DHCP release
Jan 1 00:01:19 rc_service: autodet 353:notify_rc restart_wan
Jan 1 00:01:19 stop_wan(): perform DHCP release
Jan 1 00:01:21 stop_wan(): perform DHCP release
Jan 1 00:01:25 rc_service: httpd 311:notify_rc start_autodet
Jan 1 00:01:25 rc_service: httpd 311:notify_rc start_autodet
Jan 1 00:01:27 rc_service: autodet 363:notify_rc restart_wan
Jan 1 00:01:27 stop_wan(): perform DHCP release
Jan 1 00:01:28 rc_service: httpd 311:notify_rc start_autodet
Jan 1 00:01:28 rc_service: start_autodet is waitting restart_wan...
Jan 1 00:01:29 stop_wan(): perform DHCP release
Jan 1 00:01:34 rc_service: autodet 368:notify_rc restart_wan
Jan 1 00:01:34 stop_wan(): perform DHCP release
Jan 1 00:01:36 stop_wan(): perform DHCP release
Jan 1 00:01:42 rc_service: httpd 311:notify_rc restart_wan_if 0
Jan 1 00:01:42 stop_wan(): perform DHCP release
Jan 1 00:01:44 rc_service: autodet 368:notify_rc restart_wan
Jan 1 00:01:44 rc_service: restart_wan is waitting restart_wan_if 0...
Jan 1 00:01:45 rc_service: httpd 311:notify_rc restart_wan_if 0
Jan 1 00:01:45 stop_wan(): perform DHCP release
Jan 1 00:01:47 stop_wan(): perform DHCP release
Jan 1 00:01:48 stop_wan(): perform DHCP release
Jan 1 00:01:48 rc_service: httpd 311:notify_rc start_autodet
Jan 1 00:01:48 rc_service: start_autodet is waitting restart_wan...
Jan 1 00:01:52 rc_service: autodet 383:notify_rc restart_wan
Jan 1 00:01:52 stop_wan(): perform DHCP release
Jan 1 00:01:55 stop_wan(): perform DHCP release
Jan 1 00:02:03 rc_service: autodet 383:notify_rc restart_wan
Jan 1 00:02:03 stop_wan(): perform DHCP release
Jan 1 00:02:05 stop_wan(): perform DHCP release
Jan 1 00:02:08 rc_service: httpd 311:notify_rc restart_wireless
Jan 1 00:02:08 rc_service: httpd 311:notify_rc restart_wireless
Jan 1 00:02:08 rc_service: restart_wireless is waitting restart_wireless...
Jan 1 00:02:11 kernel: Ebtables v2.0 registered
Jan 1 00:02:13 rc_service: autodet 383:notify_rc restart_wan
Jan 1 00:02:13 rc_service: restart_wan is waitting restart_wireless...
Jan 1 00:02:14 kernel: wl_module_init: passivemode set to 0x0
Jan 1 00:02:14 kernel: eth1: Broadcom BCM4331 802.11 Wireless Controller 5.110.27.20012
Jan 1 00:02:14 kernel: eth2: Broadcom BCM4331 802.11 Wireless Controller 5.110.27.20012
Jan 1 00:02:17 stop_wan(): perform DHCP release
Jan 1 00:02:19 stop_wan(): perform DHCP release


This is driving me nuts since I do related stuff for a living. ?!!

 

[jlake]

Does the SB5120 have a backup battery? If so, try removing it. Then unplug for 10 minutes.

 

[THRIZZLE]

Tried many reboots of modem (SB5120), tried cloning my laptop MAC after it was successfully connected, but nothing is working. Strange thing is that this router worked out of the box. It was not until I upgraded firmware to fix several issues that this major issue appeared.

I would recommend upgrading your modem to a SB6141. It definitely would perform better than your current modem. I recently upgraded from a similar setup and I couldn't be happier. I'm not sure if it would solve your current problem though....

 

[primitivo]

I have experienced the same symptoms as you on RT-AC56U and recent Merlin's builds. This issue has never happened before, everything was rock solid. I guess you can set your DNS settings to fixed IP - this is what I did. At least in my case the issue was not with resolving IP, but DNS from ISP.