RT-AC66U - "Your ISP's DHCP does not function properly"

[twig123]

So,

On Sunday, my Internet (Comcast) all of the sudden stopped working. I'm running a RT-AC66U that was on Asuswrt-Merlin RT-AC66U_380.59_0, but the WAN kept showing as "Your ISP's DHCP does not function properly." and "Internet Status: Ethernet WAN - DHCP Connection Failed".

DHCP on my modem is working just fine... I can power cycle the modem and connect a computer and get a DHCP lease without any issues. I also power cycled and connected a different computer... and that was able to get a DHCP lease as well without any issues. So, I have no idea why my router all of the sudden refuses to obtain a DHCP lease from my modem.

I've factory reset the router, Tried upgrading to RT-AC66U_380.63_2, also factory reset on the new firmware. Tried a 30-30-30 reset. Tried powering the modem before the router, tried router before the modem, tried rebooting the modem once the router is online. I've also tried cloning the MAC of the computer that gets DHCP, tried also statically setting the IP/Mask/GW that the computer gets assigned.... also tried reverting to completely stock firmware (FW_RT_AC66U_30043804005). Also tried enabling Dual WAN and set the secondary WAN port as LAN4, but the issue persists even with the modem connected to the secondary WAN.

I'm at my wits end... I've never had any kind of problem like this before. Everything on the router is completely functional besides the fact that the WAN won't obtain a DHCP lease.

Do I just buy new hardware and take this one out back with a baseball bat Office Space style??

Any help would be greatly appreciated.

 

[L&LD]

30-30-30 resets do not work with Asus routers.

http://www.snbforums.com/threads/no...l-and-manual-configuration.27115/#post-205573

http://www.snbforums.com/threads/rt-ac66u-slow-wan-to-lan.12973/page-3#post-269410

http://www.snbforums.com/threads/faq-nvram-and-factory-default-reset.22822/


You may need to do some of the suggestions in the second link above before you do a proper reset to factory defaults and then minimally and manually configure the router to secure it and connect to your ISP.

 

[jak8]

I have a RT68U functioning as a router connected to a Virginmedia superhub 2 cable modem which went the same way last Friday. It has been running fine for over a year no problem and just dropped. I upgraded to latest firmware which was a huge leap but still got problem with DHCP. Spent a lot of time trying to resolve to no avail.
Finally hooked up an old Buffalo unit which is functioning so far OK. So even though I accused VM of having faulty modem I presume it is the ASUS which is at fault.
Seems strange to fall over like this as it is only serving a small domestic set up.

 

[rlcronin]

Hm, well, the very same thing happened to my AC68U last night around 10PM. I tried many of the same recovery steps you all did, also to no avail. After about an hour of fiddling with it I just shut the modem and router off and went to bed. This morning I powered it all back on and it recovered.

I did notice one thing that might be a clue. Last night when I connected my PC directly to the modem to see if that would work, I ended up with an IP address in the 98.x.x.x range. This morning after everything recovered, my router got an address in the 174.x.x.x range. It seems pretty clear to me that Comcast is doing maintenance on its DHCP servers that the router is having some difficulty dealing with (that my PC did not experience). Since it is all fixed now, I can't do any further troubleshooting, sorry.

For the record, I am located in Sumter County, Florida. How about you? Perhaps this is a regional thing.
--
bc

 

[rlcronin]

30-30-30 resets do not work with Asus routers.

http://www.snbforums.com/threads/no...l-and-manual-configuration.27115/#post-205573

http://www.snbforums.com/threads/rt-ac66u-slow-wan-to-lan.12973/page-3#post-269410

http://www.snbforums.com/threads/faq-nvram-and-factory-default-reset.22822/


You may need to do some of the suggestions in the second link above before you do a proper reset to factory defaults and then minimally and manually configure the router to secure it and connect to your ISP.

Oh, and for what its worth, I did do a factory reset in the midst of my troubleshooting and could not get the Quick Internet Setup to complete. I got in to a loop with it asking me what kind of connection I had (static vs dynamic), then it would try to get a lease and fail and go right back to asking me what kind of connection I had. Over and over and over.
--
bc

 

[RMerlin]

Most cable providers will only provide a DHCP lease to the first MAC that asks for one, and will reject DHCP requests from any other MACs. Whenever moving the modem to a new device/router, you need to turn off your modem for 5-10 minutes to get the ISP to reset things on their end, and be able to once again obtain a DHCP lease.

 

[jak8]

Most cable providers will only provide a DHCP lease to the first MAC that asks for one, and will reject DHCP requests from any other MACs. Whenever moving the modem to a new device/router, you need to turn off your modem for 5-10 minutes to get the ISP to reset things on their end, and be able to once again obtain a DHCP lease.

Yes I rapidly became aware of that protocol but it had little impact even when the modem was down for a few hours. Its behaviour in my opinion was erratic sometimes providing DHCP for upto 5 to 45 minutes on the Buffalo and then dropping and refusing to provide and DCHP to the ASUS. I was pulling my hair out - what little I now have - then suddenly I switched from the Buffalo which was supposedly off line to the ASUS and hey presto I get an immediate DHCP address and the system has been stable ffor the past 10 hours.

Totally lost as to what has caused the problem. The only good thing is it encouraged me to jump up to the latest firmware having been stuck on an early version of 375 (I think) since I obtained the router. Although I have not done a rigorous upgrade as described above which I intend to do once I know things are stable with respect to DHCP.

Judging by some reports on the UK forums there are indications that there is a glitch in the Superhub which causes this problem but todate no one has identified exactly what is happening and Virginmedia pass you over to their asian backup team who demonstrate remotely that the hub functions perfectly as a router and any modem problems they claim are due to third party installations for which they have no responsibility. Nice one Virgin - bit like complaining about a car not being able to reverse but being shown it works perfectly in forward drive.

 

[rlcronin]

Most cable providers will only provide a DHCP lease to the first MAC that asks for one, and will reject DHCP requests from any other MACs. Whenever moving the modem to a new device/router, you need to turn off your modem for 5-10 minutes to get the ISP to reset things on their end, and be able to once again obtain a DHCP lease.

Ok, so that would explain what happened after I tried connecting the PC directly to the modem (i.e. why I couldn't get the router to get a lease thereafter without powering everything down overnight). But, the router was failing to get a lease even before I tried that and I had literally not touched my network configuration in many weeks. It just spontaneously stopped working. Probably when the router's previous lease expired and it went to re-up. Alas I don't have any logs that would show exactly what transpired as I did not think to keep them when I tried the factory reset in order to get things working again.

As regards the refusal of new macs issue, is there anything that can be done on the router to get it to do the equivalent of an"ipconfig /release" and "ipconfig /renew", or would that even help?
--
bc

 

[RMerlin]

As regards the refusal of new macs issue, is there anything that can be done on the router to get it to do the equivalent of an"ipconfig /release" and "ipconfig /renew", or would that even help?

That generally won't help. Once the ISP's DHCP sees a MAC, it will refuse to provide leases to any other MAC, probably to prevent abuse.

 

[Fitz Mutch]

Here's my script to get a new WAN IP address. This may or may not work for you, and you probably have a different cable modem. You're right, Comcast is probably doing network maintenance and it is causing a problem.

/jffs/scripts/new-wan-ip.sh

#!/bin/sh
# restart cable modem, and release and forget the current WAN IP
/usr/sbin/curl -d ResetReq=1 http://192.168.100.1/goform/RgConfig  # restart cable modem (SB5101)
/bin/kill -USR2 $(/bin/pidof udhcpc)  # release the WAN IP
/usr/sbin/nvram unset wan0_ipaddr # forget about it
/usr/sbin/nvram unset wan_ipaddr  # forget about it
/usr/sbin/nvram commit
/sbin/reboot

 

[tnkrer]

I am experiencing same issue on my AC-68u. No internet for a day now. Both modem and router were off during night, so turning it off for long time has not fixed the problem .. twig, did you figure out the problem or solution?

 

[Marko Polo]

Here's my script to get a new WAN IP address. This may or may not work for you, and you probably have a different cable modem. You're right, Comcast is probably doing network maintenance and it is causing a problem.

It would be very handy to build in this script analog of ipconfig /release and ipconfig /renew into Merlin. How do you think?
It's not cool to reboot the router for such simple thing.

 

[RMerlin]

service restart_wan

should work in theory (untested).