Posted: Fri May 15, 2020 21:17 Post subject: Netgear R6400v2 - Big problems
So I bought a used Netgear R6400v2 and it worked fine except I quickly found out the WAN port wasn't working. Since I couldn't figure out how to take it apart to try rewiring the port, I decided to do something even better and install DD-WRT since I had done that for friends in the past on their routers, and a quick google search told me that it had the capability to re-route the WAN port to a LAN port. Awesome!
Followed the instructions perfectly. Installed the latest firmware (which may have been a mistake?). Fired her up, and everything worked first try. Nice!
This is where things started to go wrong. I noticed that when I made selections in the settings, sometime the router would hang and need to be reset. I figured I'd better get the ports sorted before making any other changes, so off I went to Telnet to do that. Super easy, worked right away. Reset the modem twice, powered it back on and verified that the settings stuck. Cool.
Went and plugged my WAN port into LAN1, super excited to watch the fruits of my labor. No dice, no WAN detected. Reading a bit more, I found a guy who they got theirs sorted by changing the ports in the GUI as well as in the NVRAM. So I went back to the GUI and made the edits that I thought I needed to make. Hit accept and then the router locked up. Did a 30/30/30 reset and it came back but I couldn't connect to it on my PC. Did a few more 30/30/30 resets and it progressively got worse. Now after the initial lights flashing, not much happens. Generally all the lights are dark (or very dim). As I type this, my WAN light just came on and stayed on for a minute or two with zero input from me, after being plugged in for at least 5 minutes. Power light isn't on though. Basically the only lights that "work normally" are the LAN lights, but it's not like it actually establishes a connection or anything, it just detects something plugged in.
Basically it's totally messed up. I've done a lot of 30/30/30 resets and honestly it looks like they don't do anything at all. In fact, since installing DD-WRT the reset button has never really seemed to work. I saw something about it being possible to disable this button, but I definitely never touched that setting.
Is there anything I should try, or any path forward, or has my messing around with swapping ports in the settings somehow bricked my router?
If you can't telnet/ssh in and do an 'nvram erase && reboot', you may have to flash it back to stock via nmrpflash.
Wow that was quick, thanks! Ok, I'm almost positive I didn't use the proper firmware. I knew I was accepting some risk in using DD-WRT, but I didn't realize that I was doing something foolish. I just followed the link in the instructions, presumably to the router database.
Also didn't realize I had an ARM chip, didn't mention anything about that in the instructions, so that's my bad. I'll tackle all of this new info when I have time and we'll see if I can salvage my router. FWIW, I got my money back for it, so it's not like it's the end of the world, and it had already suffered at least one hardware failure so it's not like this is a huge loss.
Last edited by darkpuma on Fri May 15, 2020 21:40; edited 1 time in total
Joined: 08 May 2018 Posts: 14217 Location: Texas, USA
Posted: Fri May 15, 2020 21:38 Post subject:
If by "latest and greatest" you mean 40559, then yes. If you mean 43136, possibly not. You probably need to reset it properly... worst case is is you flash back to stock with nmrpflash. Not sure this one has the reset button trick for TFTP. _________________ "Life is but a fleeting moment, a vapor that vanishes quickly; All is vanity"
Contribute To DD-WRT Pogo - A minimal level of ability is expected and needed... DD-WRT Releases 2023 (PolitePol)
DD-WRT Releases 2023 (RSS Everything)
----------------------
Linux User #377467 counter.li.org / linuxcounter.net
If by "latest and greatest" you mean 40559, then yes. If you mean 43136, possibly not. You probably need to reset it properly... worst case is is you flash back to stock with nmrpflash. Not sure this one has the reset button trick for TFTP.
You're replying too quickly!!
I edited my post. Yeah, looking back, I loaded r43136.
Thanks so much for the help, cheers!
-edit-
Ok so I learned a few things. I was doing the hard reset wrong. I followed the flashing instructions so that worked fine, but after I made the changes to the ports I started trying to hard-reset it wrong (using the reset button). I also just learned that I have a WPS button lol... so now hard resets are super easy, but they're not working offhand. Once again, I'll try again later, I seem to have slightly different LED results each time I power the router on... with a bit of luck I'll eventually get it.
Well I'm reasonably sure that all my messing around has led to a serious hardware failure.
Now no matter what I do, or what type of reset I try after pressing the power button a few lights flash and go out. The power LED never comes on full brightness, and stays very dim amber.
++edit++
Ok I've discovered I can get a couple pings from the router IF i plug a cable into either port 2 or 4 and hold the reset button and press power (once or twice) until getting a reaction from the LEDs. Then the power LED will stay on with the LAN port LED. The pings stop after a few seconds.
I can't repeat this behavior more than once without swapping between port 2 and 4 lol. Will not work at all if a cable isn't plugged in. This thing is so messed up. Not sure if it's worth buying that cable or not, I'm guessing no.
Joined: 08 May 2018 Posts: 14217 Location: Texas, USA
Posted: Thu May 21, 2020 2:25 Post subject:
Check if it's looking for anything via Wireshark. You should be able to nmrpflash stock firmware back to it, if it responds to ping. Should also be able to TFTP, but nmrpflash usually works better. Sounds like you are being impatient and doing 5 things instead of one. _________________ "Life is but a fleeting moment, a vapor that vanishes quickly; All is vanity"
Contribute To DD-WRT Pogo - A minimal level of ability is expected and needed... DD-WRT Releases 2023 (PolitePol)
DD-WRT Releases 2023 (RSS Everything)
----------------------
Linux User #377467 counter.li.org / linuxcounter.net
Check if it's looking for anything via Wireshark. You should be able to nmrpflash stock firmware back to it, if it responds to ping. Should also be able to TFTP, but nmrpflash usually works better. Sounds like you are being impatient and doing 5 things instead of one.
I wouldn't say that it's because I'm getting impatient, I'm just completely confused as to what's going on at this point.
The way I'm allegedly supposed to reset the router is holding the reset for 10s once it's on. For me, this does nothing, and furthermore, it never really "turns on".
The only way I can prompt a response out of the router now (aside from a single flash of lights and then nothing), is to hold the reset button while starting the router with a cable plugged into select LAN ports. I'm completely off the beaten path here, and I have no idea why this works, or why it only works like every 1/5 times. When it does this, I get dancing lights once or twice, then a solid amber power LED. During the dancing lights, I can get some pings from the router for a few secs.
After I recognized that I could get pings for a few seconds in this 1/5 case, I tried TFTP. Not 100% sure I did it right, but I followed the instructions and ran it the second the lights started dancing which should theoretically have corresponded to pings. It hung for a while and then gave me a no response error of some sort. I wasn't really surprised by this, because the instructions indicated it probably wouldn't work.
What would I be looking for in Wireshark, and how would it help? Sorry, I'm a noob
If you think I have a good chance of saving it with nmrpflash I'll go ahead and buy the cable. It's only like $3 of ebay, so can't hurt to try I guess.
Joined: 08 May 2018 Posts: 14217 Location: Texas, USA
Posted: Thu May 21, 2020 13:05 Post subject:
If this particular router has it, what you are doing by holding the reset button while powering up is putting it into TFTP mode. That is IF this router operates that way. Which means you should be able to push firmware to it.
Otherwise, it should boot up if all went well with de-bricking. Worst case is that you need to attach serial adapter and see what it's doing via serial console. If you do serial, you need to verify the pinout and only attach TX, RX, and GND. You do NOT attach the Vcc lead or you risk damaging the router.
Wireshark is a packet analyzer. You would be able to see what packets the router and your PC/laptop are passing out to the network. I presume you are doing this with the router completely removed from the network with only the PC/laptop you are using to de-brick connected?
I think perhaps the only thing you did not do is telnetenable in stock firmware to see what boardid your unit has to pick the right firmware image, not sure if that is what bricked your router. _________________ "Life is but a fleeting moment, a vapor that vanishes quickly; All is vanity"
Contribute To DD-WRT Pogo - A minimal level of ability is expected and needed... DD-WRT Releases 2023 (PolitePol)
DD-WRT Releases 2023 (RSS Everything)
----------------------
Linux User #377467 counter.li.org / linuxcounter.net
If this particular router has it, what you are doing by holding the reset button while powering up is putting it into TFTP mode. That is IF this router operates that way. Which means you should be able to push firmware to it.
Supposedly it doesn't work well (if ever) with mine. Haven't seen any success stories.
Quote:
Worst case is that you need to attach serial adapter and see what it's doing via serial console. If you do serial, you need to verify the pinout and only attach TX, RX, and GND. You do NOT attach the Vcc lead or you risk damaging the router.
Serial cable should be here in a month or so lol
Quote:
Wireshark is a packet analyzer. You would be able to see what packets the router and your PC/laptop are passing out to the network. I presume you are doing this with the router completely removed from the network with only the PC/laptop you are using to de-brick connected?
Correct, and I'm familiar with what it is, but I don't know how it will help. Is there a tutorial you could link me to? Btw, thank you so much for all your help, it is really appreciated!
Quote:
I think perhaps the only thing you did not do is telnetenable in stock firmware to see what boardid your unit has to pick the right firmware image, not sure if that is what bricked your router.
I did telnet in the stock firmware, noted the boardid, made full backups, logged everything, etc. It didn't seem to help me though/hasn't helped me yet
I'm reasonably sure what bricked my board was all the 30/30/30 resets. It wasn't working great before that, but at least it was working. After the 30/30/30 resets it got progressively worse (rather than better) until we got to where I am now.
Joined: 08 May 2018 Posts: 14217 Location: Texas, USA
Posted: Fri May 22, 2020 2:15 Post subject:
Yes, and this is one of those routers that are the reason why you DON'T do a 30-30-30 reset on them, because you risk bricking it. I don't know of any "tutorial" for Wireshark in general, sorry. The packets usually are color-coded for type of packet, etc. and should be obvious as to what each packet is. Hopefully, you can get this thing revived with a little time and patience. _________________ "Life is but a fleeting moment, a vapor that vanishes quickly; All is vanity"
Contribute To DD-WRT Pogo - A minimal level of ability is expected and needed... DD-WRT Releases 2023 (PolitePol)
DD-WRT Releases 2023 (RSS Everything)
----------------------
Linux User #377467 counter.li.org / linuxcounter.net
Well I'll be. After nearly giving up several times I successfully unbricked it via the serial cable
Some lessons learned: THE UNBRICKING GUIDE v1.33 HAS ERRORS that if corrected will make a world of difference to making it easier to follow.
1) It tells you to connect the serial cable improperly. Fig 7 is correct, but is improperly described. It inadvertently says connect G to G, T to T, and R to R. After some confusion and reading a different set of instructions, I realized I had the T and R wires mixed up. The cable's T goes to the routers R, and the cables R goes to the router's T. Duh/whoops!
2) Need to go into your device manager and make sure your cable settings match what you're putting into PUTTY (as shown in figure 9). Not sure how important this is, but it's probably worth doing.
3) Putty will not allow you to launch the serial connection from the window described in the instructions if you have not set the "Session" tab properly. Correct steps: Go to session tab, select serial, and select the appropriate COM port. save the session. Then go down to the SERIAL tab, set everything as described and THEN hit open. If you haven't clicked SERIAL in the SESSION tab when you click open nothing will happen -> Noob mistake, but still, could be clarified.
4) Router WILL NOT BOOT with the USB cable plugged in. All lights will come on, but nothing will happen in putty. Correct sequence: Power On, Immediately plug in USB cable, as soon as it's detected (1-2s) hit OPEN in putty to get things rolling. If you're not quick enough you will miss your opportunity to hit CTRL-C to get to the CFE> prompt.
5) This is what stumped me for a long time. I could ping the router easily now, but could not get nmrpflash or TFTP to connect. As it turns out, this is because the router wasn't expecting anything.
Use Windows built in TFPT as described at this stage, I have confirmed it works fine. No need to use NMRPFLASH. Go back to Putty. at the CFE> prompt, type "tftpd" and the router will tell you it's starting it's TFTP server. AHA. NOW go back to your command prompt and try the tftp command to flash the firmware... and bingo.
But this was only half the battle. Now I have a working router, but it still has the hardware failed WAN port. Now to try and fix that for the second time, without bricking it through dozens of bad resets
Wish me luck, and thanks again for all the help!
-edit-
My excitement was short-lived. After I got the router working again, and got into the web interface, I changed the password, got to the main screen and then I wrote this post. When I went back to the web interace, the router had apparently locked up, and was unresponsive. I restarted it, and all the lights come on (like they did when I was plugged in via serial and nothing would happen) and now I'm back to square 1. WTF I'm starting to think either the firmware is bad or the router has a corrupt memory or something.
Last edited by darkpuma on Sat Jun 13, 2020 15:46; edited 1 time in total
Joined: 08 May 2018 Posts: 14217 Location: Texas, USA
Posted: Sat Jun 13, 2020 15:43 Post subject:
And you wonder why I linked the Serial Recovery wiki. Glad you got it sorted out. Not sure what your issue with the WAN port was, but feel free to re-describe it, post properly-sized screenshots as required, etc. https://wiki.dd-wrt.com/wiki/index.php/Switched_Ports might help you determine what might be going on if there is something amiss in the nvram settings. _________________ "Life is but a fleeting moment, a vapor that vanishes quickly; All is vanity"
Contribute To DD-WRT Pogo - A minimal level of ability is expected and needed... DD-WRT Releases 2023 (PolitePol)
DD-WRT Releases 2023 (RSS Everything)
----------------------
Linux User #377467 counter.li.org / linuxcounter.net
And you wonder why I linked the Serial Recovery wiki. Glad you got it sorted out. Not sure what your issue with the WAN port was, but feel free to re-describe it, post properly-sized screenshots as required, etc. https://wiki.dd-wrt.com/wiki/index.php/Switched_Ports might help you determine what might be going on if there is something amiss in the nvram settings.
Yeah, it's not working again (see my edit).
Either I've got a hardware/memory issue, or the router just doesn't like the dd-wrt r43136 firmware.
Now when I power it up all the lights come on and stay on. Can't connect via Serial cable anymore. No type of connection via ethernet at any point (no lights/network cable unplugged).
I was so happy a minute ago, and now I'm just so frustrated. I recovered it perfectly, and then minutes later it was back to an entirely different and seemingly even more unrecoverable state without even touching any settings. Any thoughts? ARRRG!
Note: when the issue first happened, I tried doing a reset as described in the unbricking guide, and that didn't do anything.
-edit-
One last thought - this router clearly doesn't want to be saved. Going to take a break for a bit, and retrace my steps. If I can't get it to connect via serial or ethernet there is clearly nothing I can do to save this thing, so I'll probably just chuck it.
I knew I was accepting some risk in using DD-WRT, but I didn't realize that I was doing something foolish. I just followed the link in the instructions, presumably to the router database.
Glad you got it sorted out. Not sure what your issue with the WAN port was, but feel free to re-describe it, post properly-sized screenshots as required, etc.