dd-wrt WAN DHCP and R8000 vs wndr4500

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unimorpheus
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dd-wrt WAN DHCP and R8000 vs wndr4500

========Long post: Sorry but there is a lot of background. Below was posted in a DSLreports forum but the issue was originally posted here under the WNDR4500v1 forum when I was troubleshooting that device.========

 

I have had Charter cable since about 2008 and after a bad period between 2008-2009 is had been rock solid. Almost like a real utility, always on. Fast forward to 6 weeks ago and it has become nearly 100% unreliable. for the past 4-5 years I have been using a Motorola SB6120 modem and Netgear wnd4500v1 router running dd-wrt. This setup just worked, no issues at all. Out of no where started having problems. After extensive troubleshooting I began to notice consistent WAN DHCP issues. Where I used to get a dynamic IP assignment that would last for weeks I was now getting leases that were as short as 1 hour with nothing greater that 6 hours for weeks.

The problem initially started with incomplete DHCP where I would get WAN ip, subnet and gateway but no DNS. To counter I configured the router with a static openDNS DNS assignment. Eventually I stopped getting DHCP addresses at all from the modem almost as if the WAN port on the router had died. I found that if I cycled the WAN port from active to disabled back to active DHCP I would get a complete DHCP assignment but again with a short 1 hour lease. When the lease was up the connection would drop. No new lease. Sometimes the connection would be up for days without issue then bam, can't get an address.

Suspecting old gear was the problem I replaced the power brick on the router which tested good with no load. No impact on the problem. Checked the power brick on the modem and found it was providing 14.4vdc when it should have been 12vdc. Replaced. Charter tech stated signals from the Motorola modem improved with the new power brick but were still marginal. I suspected the 14.4vdc damaged the modem. Yesterday I replaced the Motorola modem AND the router. I had an old DOCSIS 3.0 Ubee modem from Charter that I never used since I had the Motorola. I also purchased and configured a new Netgear R8000 with the latest dd-wrt firmware.

This configuration it worse than the old setup. After a few hours the router just stops responding. At lest with the old wndr4500 the LAN side of the router would continue to work perfectly even when the WAN was down. I could dial into the 4500 to look at the WAN config and see it was not getting an assignment. With the R8000 LAN and WAN just stop responding. Charter support claims the modem looks good but can't explain the change in WAN DCHP assignments and why the modem will not acknowledge DHCP request. I have a serial connection configured on the wndr4500v1 and can watch the unanswered discovery request sent to the modem.

The only thing in common at this point is dd-wrt as the modems have been changed and routers swapped. I currently have the old 4500 router in place as it is more reliable than the new R8000 which freezes after a few hours. As a last test I will re-flash the old 4500 with the oldest dd-wrt I can find to see if something changed with the new builds but I can't do that with the R8000 as everything is new with that router. I still think Charter has changed something in their network config that is breaking dd-wrt routers. Connecting laptop directly to modem via a switch always works. I have not tried re-flashing the R8000 router back to Netgear firmware an may test that this weekend. Does this sound familiar to anyone?