T3/T4 Timeouts/Ranging Request issues - modem reboots frequently

Think of T3 and T4 errors as just different flavors of the same thing; communication problem between the modem and Cox in the language (DOCSIS) that the modems use. Like a Marko/Polo game.

T3 = "The cable modem has sent 16 Ranging Request (RNG-REQ) messages without receiving a Ranging Response (RNG-RSP) message in reply from the CMTS." So modem said "Marko!" 16 times and haven't heard "Polo" from Cox. So it resets to try the process again. This is usually because Marko isn't talking loud and/or clear enough, AKA the upstream signal to noise ratio (US/TX SNR) isn't good.

T4= "The cable modem did not received a station maintenance opportunity in which to transmit a Ranging Request (RNG-REQ) message within the T4 timeout period (30 to 35 seconds)." So modem didn't even get the chance to say "Marko" for 35 seconds. Think of this like Marko falling underwater and not even getting a chance to yell. This is usually caused by the signal completely stopping (outage) or the signal coming into the modem not being loud and/or clear enough. For more info see here.

So the first thing I would check for is your downstream signal SNR. To simplify it just post the signal levels you find on the 192.168.100.1 page and we can decipher them. If that address doesn't work, reply with what model modem you have and I can give specifics. 

Thanks for the quick reply. 

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Here's the log. It basically just does this over and over again. When the time reads "1970", thr modem is rebooting 

Looks like ingress on the 23.3Mhz range which could be someone's HAM radio. Do you know of any large antenna's around you?

Not that I know of, but I'll take a look around when I get home.

Problem just started out of the blue a few weeks ago.  Initially figured it was just my modem calling it quits, took it as an opportunity to upgrade.

In the event it is antenna interference, what is the solution?

MJS1982 said:
In the event it is antenna interference, what is the solution?

First allow me to correct myself. 23.3 is sometimes used by HAM radio, but it looks like its specifically destinated for airport landing stip equipment. See below or here for more info. Any airports around?

23.2 - 23.35 MHz
FIXED 5.156A 
AERONAUTICAL MOBILE (OR)

Second, as for what you can do, it depends on what you find. If it is a airport, and they are broadcasting within their legal rights, then its better to find where the signal is leaking IN to the line. A cable wire is basically a long RF antenna, and any break in the protective coating around it, or a issue with a splitter connecting them, can pick up any bad frequency that happens to be going through the air. However if you find that the broadcast is like from some home made equipment, you could call the FCC and report it. If its a neibor you might just want to ask them to stop or tell them your issue, incase its just a innocent mistake.

Last, keep in mind this is just my guess what the problem is. Unless the source is obvious, and as long as you ruled out any inside wiring issue, its really the technician job to find any possible ingress (signal) and track it down. Or it might be a totally different problem. I was just trying to think outside the box. Still have to think INSIDE the box too. 

READ THIS FIRST

Did some more digging and found 23.3 is also a frequency used in Broadband over Power Line (BPL) also known as Power line. Do you have anything like that? It would be a network adapter you would plug into a electrical socket and be used for networking via your electrical wires. If so, you might have a bad ground and it's back feeding into the cable. I would think this is more likely than a nearby airport.

Sorry for delay; been a busy week.

I don't have the BPL Health Edge mentioned.  The airport is several miles away, but I've never had any issues before a few weeks ago.

Really appreciate the responses; think I'm going to have to have a tech come out and see what's what.  After two modems and two routers, I'm doubting it's the equipment.  The modem plugs into a standard coax which runs up the wall, through the attic, and out to the telephone pole.  I know at least some of the coax in the house has probably been there for a long time.  Thinking it's cruddy wires, a bad connection at the phone pole, or something bigger down the line.

I'll post back once the tech comes out.

Thanks

Typing this out on my phone; Internet still not working. Two techs and a maintenance tech have been out. No closer to figuring this out. Equipment is fine, and when the connection is up, it's fast. But it's generally only up for 2-3 hours a day at this point (in case you were wondering, yes, the Cox bill is still right on time...)

maintenance guy said there's something choking up the line, but can't figure out where it is. He was working until 8 or 9 last night and was back at it this morning around 8. 

Apparently my house is the only affected. 

This is really infuriating. I've been reading other posts about the same issue with other providers in other markets, and nobody seems to have a solution. Not really sure where to go next. 

I am having this problem, just as you describe it. I have had it for months and final decided this week to try to figure it out because it is getting worse. A contract tech came to my house today and said that everything was fine -- he replaced some splitters. Two hours later it was clear that the problem remains.

I have been reading up on this problem and can see that my modem is rebooting many times a day, just after the upstream power goes too high for reasons unknown. I told the tech about the power problem and he did not seem to care. (in fact the tech did not seem to know about modem logs). It took me literally 10 calls to Cox to finally get to a person with an IQ high enough to understand the problem (gratefully that person was pretty smart). I requested that they send someone on the "A" team rather than the "C" team on Friday when they come back.

You know, I have been a Cox customer for a really long time, like 22 years. I was one of the first broadband customers in Omaha. I have never had problems like this with Cox before. (In fact, when people complain about Cox I have noted internally that I have had no such complaints, until now). I hope this is not a sign of decline since I don't have another option in this part of town except the unbelievably pathetic CenturyLink that boasts I can get up to 1.5 megabits at my address. (wow)

I may buy a new modem tomorrow just to see if it helps. I have an older motorola Surf Board 6120, which seems to be causing many people problems.

Any one else out there have thoughts about this?