Trouble with Motorola SB6141 Docsis 3.0 modem and T3 errors.

If you are unable to access the routers 192 page when your problem occurs then there is a issue with your router. Even with your modem unplugged you should still  be able to access the router. Sounds like maybe its resource crashing. What kind of router do you have?

Asus RT-N16 with DD-WRT v24-sp2 (08/19/13) vpnkong installed.

I had no troubles with this router before installing the new modem, and the issue occurs even if I connect a computer direct to the modem and power-cycle it. So I'm pretty sure it's not an issue with the router, but I can't explain away this strange behavior. I should note that even with the computer directly connected to the modem, I cannot access 192.168.100.1 until the modem eventually starts behaving again, at which point everything is fully functional.

Even if the router isn't the issue, its still the first step in finding the problem. There are other reasons why connecting direct to a modem won't work (static IP, needing to power cycle modem for new IP, Windows network discovery, etc) so that doesn't rule the router out at best it only confirms that its ALSO a problem.

When it happens focus on the routers gateway. First disconnect the modem from the router entirely and see if that fixes it. Maybe its trying to aquire a new DHCP and freezing? If that doesn't give you access try telnet/port scan the gateway IP and ping it. Also check logs out at http://192.168.1.1/user/log.html  (atleast that is the default)

I also looked at your logs and don't see anything bad. The only critical occured when Cox sent a reboot signal. 

PS. Might want to edit your post to remove MAC addresses.

Unfortunately I am unable to edit the original post, in my haste I failed to notice they contained MAC addresses, oops.

Any idea who I should contact to remove the images?

In the meantime, I found this post: http://www.dd-wrt.com/phpBB2/viewtopic.php?p=716161

I was unaware that the SB6141 was a router/gateway/etc device, I thought it was just a modem, I have changed my router to operate off of 192.168.3.1 (192.168.2.1 is being used by something else) and I'll see if that helps. At this point, I really am not sure what the cause is, but you guys are right, I'm putting my money on the router, because I just can't think of any other reason why I wouldn't be able to access it or the modem when this issue occurs.

Maybe click "Report Abuse" below it? That should flag someone. 

As for the SB6141 its NOT a modem/router gateway, who told you that? ::ponder::  It should be giving what ever device is connected to it a public IP. The only other IPs that should show up from the modem is 192.168.100.x, and thats only if the modem cant connect to the DHCP server, and usually the modem goes offline when that happens, so its rare.

At this point, I'm desperately reaching out for a solution. Somebody in the forum post I linked said something of the sort. It's the only thing I can think of at this point.

So far everything's working, *knock on wood*, but I'm keeping an eye on things, this is a sporadic problem, so, I can't be sure it's fixed.

At your suggestion, I've replaced the ethernet cord, I'd be surprised if it was the modem, as it's brand new. Unless my internet is out, I'm able to connect to the modem either through the router or directly, but once the connection goes out, nothing is accessible, which makes it sound like a router problem or a routing conflict, which I'm hoping is the case, as I've taken steps that should fix it.

Last time this happened, I unplugged my router, plugged it back in, and almost immediately the problem was resolved, normally this takes 5-15 minutes to fix itself, more and more signs are pointing towards a network problem, not a modem problem, and as I mentioned, I've taken steps that *should* resolve the issue, but I'll need a day or two to know for sure.

One thing that remains unexplained, however, is why my download speeds seem to pin at 32.5 or so Mbps and why my upload speeds have nosedived to a pitiful 3-4 Mbps, where they were anywhere from 5-10 with the old DOCSIS 2.0 modem.

I'm on the premier plan, if memory serves, which is now 50 Mbps down, and I want to say... 10 Mbps up? Maybe more.

He cant access the modem when this occurs because the router is crashing and thats between the computer and modem. Its also been stated that just power cycling the router fixes the problem. Also, when it occurs he cant access the router OR the modem. This all points to a router issue. 

Have you checked the logs on the router?

I am reasonably sure that this is the case, because it's the only thing that makes sense. I've updated my router and done a factory reset, tweaked some settings, and my network has behaved thus far. Nothing worrying in the logs since I did a factory reset, didn't check beforehand.

Gonna give it a few days and then call it fixed. My download/upload speeds still seem screwy, though.

Well, my internet is about as solid as it ever was now, but I'm still not getting the speeds I should be getting after that upgrade. My download speed is pinned at about 32.5 Mbps, when it should go up to 50. My upload speeds are locked around 3-5 Mbps which is worse than it was before the upgrade. I talked to CSR live chat, and they reset the modem, said to come back if that didn't fix it.

Any other ideas? I don't want to have to have a technician come out and look at it if I can fix it myself, or if Cox can fix remotely.

Yes, I rebooted the modem and saw an immediate difference! Getting 60 Mbps down, 11 Mbps up, you are the man, Chris! Thanks a bundle!