Posted: Sat Jul 16, 2022 16:04 Post subject: WRT1900ACS V2 no WAN DHCP after power outage
WRT1900ACS V2 running DD-WRT v3.0-r39884. Power went out during a storm and when power was restored the router could not obtain ip via dhcp from cable modem (Arris SB6183). I tried all of the various reboots, power downs, leave unplugged, etc. solutions everyone offers in the various threads here for this situation. Everything else seemed functional so I thought the storm had killed the WAN port on the router. Tried another router on the cable modem and confirmed that was working ok. Since I thought the WAN port had died I started trying to figure out how to reconfigure one of the LAN ports to be used for the WAN port (I had tried to do that with a WRT1900AC and failed some time ago but I figured it was worth a try). At some point during this I managed to switch boot partitions and the router booted to stock firmware. I happened to have the cable modem connected to the WAN port when it rebooted to stock firmware and to my surprise the router got an ip via dhcp from the modem! So the WAN port wasn't dead but for some reason DD-WRT is unable to obtain ip via dhcp while stock firmware can. Since this discovery I have tried even more variations of reboots, connects, disconnects, several different versions of DD-WRT all with no success. I can still boot to stock and it works fine but I have tried multiple DD-WRT releases up to r49392 without success. I am happy to provide whatever additional information might be needed to help troubleshoot this problem. I have read many posts on here with similar problems but where there was a solution found, those solutions do not seem to be working for this router.
Have you tried recovering your configuration from a dd-wrt backup, and if that didn't work then resetting it to dd-wrt factory defaults? _________________ My DD-WRT Routers:
Linksys WRT3200ACM - Marvell
Linksys WRT1900ACS - Marvell
Netgear R9000 - Atheros
Netgear R7000 - Broadcom
PC x86-64 VM - Atheros
One additional piece of information I forgot to include... I tried connecting the WAN port of the WRT1900ACS (running DD-WRT) to one of the LAN ports on my other router while the other router was connected to the modem and the WRT1900ACS got an ip address from the other router.
modem -> other-router -> WRT1900ACS - dhcp works.
It is as if something changed for my isp during the power outage and now my WRT1900ACS when running DD-WRT cannot correctly negotiate dhcp with the isp (but can do so with other dhcp servers apparently).
Not my forte, but here's an idea: Is your modem handing out DHCP addresses to both routers, or is it merely acting as a switch? Most ISPs want to see a single IP from one client, so you'd probably want to double-NAT (by enabling DHCP on the modem, if possible) to get both routers to reliably connect in parallel to the modem. Otherwise you may have a race condition where the ISP might see one router first and not hand out or recognize an address from the other. _________________ My DD-WRT Routers:
Linksys WRT3200ACM - Marvell
Linksys WRT1900ACS - Marvell
Netgear R9000 - Atheros
Netgear R7000 - Broadcom
PC x86-64 VM - Atheros
" Most ISPs want to see a single IP from one client, so you'd probably want to double-NAT (by enabling DHCP on the modem, if possible) to get both routers to reliably connect in parallel to the modem."
Sorry, didn't mean to confuse my issue. I am only connecting one router to the modem. If I connect an old back up router, it gets dhcp ip without problem.
modem -> other-router - dhcp OK
If I connect WART1900ACS running factory firmware it gets dhcp ip without problem.
modem -> WRT1900ACS(factory fw) - dhcp OK
If I connect WRT1900ACS running DD-WRT firmware to modem dhcp does not give ip address.
modem -> WRT1900ACS(dd-wrt fw) - dhcp NOT OK
If I connect WRT1900ACS running dd-wrt firmware to other router it get dhcp ip (from other router) address ok.
modem -> other-router (dhcp OK) -> WRT1900ACS(dd-wrt fw) (dhcp from other router OK).
All of this tells me there is some incompatibility between dd-wrt firmware running on WRT1900ACS and my modem/ISP. Also, the other router I am using also has dd-wrt firmware (but of course the other router is not a WRT and actually not even a LinkSys). So it is just the combination of my Arris modem/ISP + WRT1900ACS + dd-wrt firmware. The strangest thing to me about this whole situation is it only started happening after the power outage. Prior to that the WRT1900ACS had been running dd-wrt fine for at least 2 years.
Power down the ISP modem and your router. Wait 5 minutes. Power up ISP modem, let it completely boot up and sync with your ISP. Power up your router. _________________ "The woods are lovely, dark and deep,
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep." - Robert Frost
"I am one of the noticeable ones - notice me" - Dale Frances McKenzie Bozzio
"Power down the ISP modem and your router. Wait 5 minutes. Power up ISP modem, let it completely boot up and sync with your ISP. Power up your router."
I've tried that and all of the other recemmended ways of powering down, powering up, waiting with things unplugged, in various orders, etc. I have tried everything I could find in the various threads even in the non-Marvell sections of the site. Behavior is exactly the same in all cases.
When I run "udhcpc -i eth0" from a telnet session this is all the output I get:
Did you also try different ethernet cables to rule out a bad cable? Worst case is having to contact the ISP to ensure that the WAN mac of your WRT1900* is registered on their system properly. That's all I can offer besides exercising a little patience and ditching any hint of stock firmware on your router. There is also a slight possibility that your WAN port or the modem's LAN port got bit by a surge. _________________ "The woods are lovely, dark and deep,
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep." - Robert Frost
"I am one of the noticeable ones - notice me" - Dale Frances McKenzie Bozzio
Joined: 04 Aug 2018 Posts: 1444 Location: Appalachian mountains, USA
Posted: Mon Jul 18, 2022 17:21 Post subject:
I may as well say it, as someone has to...
You say you are on build 39884, which is ancient. Try the current build, not the router-database one (which is irrelevant), but the current one (but check its new-build thread in this forum first, just in case). You'll need to reset the config after flashing (the recessed red button on the back, for a few seconds, until the lights start to flash) and laboriously re-build your config, because of the particular huge jump in builds. Too much has changed internally to just keep your old nvram contents as they are.
Irrespective of your current DHCP/WAN issue, you'll want to update the build just to get the many security improvements. _________________ 2x Netgear XR500 and 3x Linksys WRT1900ACSv2 on 53544: VLANs, VAPs, NAS, station mode, OpenVPN client (AirVPN), wireguard server (AirVPN port forward) and clients (AzireVPN, AirVPN, private), 3 DNSCrypt providers via VPN.
So the WAN port wasn't dead but for some reason DD-WRT is unable to obtain ip via dhcp while stock firmware can. Since this discovery I have tried even more variations of reboots, connects, disconnects, several different versions of DD-WRT all with no success. I can still boot to stock and it works fine but I have tried multiple DD-WRT releases up to r49392 without success.
Disregard my comment about possible hardware failure. The only thing I can possibly think of is a key difference in DD-WRT and stock that is causing an issue, but as was already stated above, if you are not on the current DD-WRT release, then the likelihood of finding a solution isn't that great. Neither is maintaining a partition with stock firmware on it going to help you because of a single shared NVRAM partition on these devices. Having a recovery option by doing this is a moot point. _________________ "The woods are lovely, dark and deep,
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep." - Robert Frost
"I am one of the noticeable ones - notice me" - Dale Frances McKenzie Bozzio
"You say you are on build 39884, which is ancient. Try the current build," and "but as was already stated above, if you are not on the current DD-WRT release, then the likelihood of finding a solution isn't that great."
I guess you guys missed the part in my original post where I said "I have tried multiple DD-WRT releases up to r49392 without success."
Also, I have tried different cables. I have tried everything that is normally suggested including getting rid of Factory firmware on the other partition. As I said in my original post, if it has been suggested in another thread somewhere I have tried it. I am currently maintaining the Factory firmware on one of the partitions because I do need an internet connection to do my day job (software engineer). Yesterday I finally started trying to track down source code for udhcpc so I can unravel the problem myself. It appears to me when udhcpc runs it gets stuck after the second "sending discover". Looking the code I have found so far I am not sure how that happens.
Thanks for all of the suggestions, I have tried them all with zero change in the results so far.