Cable Modem Keeps Resetting

[chevyordeath]

Ok - I have no idea why, but my cable modem resets ALL the time. It is really sporadic, sometimes I can go hours without it resetting and some times it resets 2 or 3 times within a half of an hour. I have had the cable company out a dozen of times. I have had my modem replaced twice, my router replaced twice, my splitters replaced and all of the lines checked - still an issue. So finally today another tech was out, he was carrying around this weird meter that had 2 antennas sticking out of the sides - he said he was checking for "leakage" what ever that means. Long story short, his meter was going bat **** in my room where the cable modem is. He disconnected the cable to my house from the box, it was still going off. He told me that if there was a problem with their equipment or something in the lines at that point it should have stopped. SO he told me that the issue must be power related. So we shut off my belkin surge protector and the meter shut up. I turned my PC back on and the meter started going off like crazy again. He said the problem was my computer, that it was giving the modem feedback or something. Has anyone heard of something like this? Is the problem my computer, or the power that goes to it? Would a battery backup or something fix this issue? Is this even likely the reason my modem keeps resetting? Sorry for all of the questions but this is driving me nuts and I'm sick of dealing with my cable company. Thanks guys.

[Roger H. Veteran]

Sounds like it's loosing sync. I'm sure they checked that but what are your signal levels in the modem? Are you on Comcast or what? try http://192.168.100.1 and see what it says.

[chevyordeath]

Mediacom.

Name

DPQ2160

Modem Serial Number

228242441

Cable Modem MAC Address

[edited per request]

Hardware Version

2.0

Software Version

dpq2160-v202r12811-090120as

Receive Power Level

-6.0 dBmV

Transmit Power Level

49.0 dBmV

Cable Modem Status

Operational

It's a Cisco (Linksys with Cisco name on it) modem. Brand new.

They check my signals every time and tell me they are good.

[Steven P. Administrators]

Should see if your PC case is connecting to anything electrical like the motherboard or anything else.

[+BudMan MVC]

Was he checking for EMI/RFI? When you say it went away when you turned of the surge protector - did this also shutoff your computer? And then when you turned on the computer you were not using the surge, or did that get turned back on as well.

I guess it would be possible maybe your computer PSU is putting out too much EFI? Or could be a fault on your house electric causing all kinds of issues?

Had a wiring issue in a building once that caused all the battery backups to go crazy! Beeping all the time, etc. It was one device that was causing a problem on the electric.

If your saying happens just when your computer is turned on you might want to look into having the powersupply checked or replace it with a spare do you still have the problem?

When you say the modem resets do you mean the lights flicker or go off on it and then back on, or your just saying you loose internet (sync) Not talking the normally blinking but actual reset where it boots up again. Like when you pull its power plug. I find it unlikely that a sync issue would cause it to actually reset, and would think it more of a power related problem.

Do you have any sort of meter you could put on your power, some battery backups have built in meters and software to monitor voltage, current, and would report either low power (brown out) overpower, ground faults, etc. etc.

Depending on the UPS you get their are some that completely isolate the devices from the actual power line and run off battery at all times, etc. You might want to invest in a good UPS even if you were not having current power issues. A good UPS is better than just a surge protector, keeps the voltage supplied to the devices constant be it if input is too low or too high, etc. I would then connect your modem to this as well as your PC and or any switches and monitor. Added feature of this is even if you have a complete power outage you would still have internet :) for the whatever your run time is on your UPS.. Which depending could be like an hour and would allow you to use the internet while power is out for short periods ;)

[fusi0n]

I wouldn't keep your mac address up there.. people can clone that and activate their modem from yours

[chevyordeath]

@ BudMan

Yes, my PC was plugged into the surge protector. When we turned the surge back on the meter was fine, but when I powered my PC back on it jumped, and after POST it started going off bad. The modem actually resets, the lights turn off, then they flash back on one a time like you unplugged it and plugged it back in.

I suppose my PSU could be going bad, but I do not have a spare - and haven't had any issues with my PC itself at all. I was thinking about picking up a UPS today at Best Buy to replace my mid-level Belkin surge protector. Any recommendations?

@Fus10n

Good point, I didn't even notice that MAC was in there when I copied that in. The forum is only letting me edit my first post. Could I get a mod to delete my MAC from that - my mistake.

Thanks guys.

[+BudMan MVC]

As to the mac thing - I really woundn't worry about it too much.. For starters I don't know of a way to edit the mac of the actual "modem" Sure you could change the mac on the interfaces of a router - thats not going to get them anything.

And even if they could change it - the company is not going to allow the same mac on their network.. And registering the mac would not charge your account or anything, so I don't see how it could be an issue to be honest.

As to a good UPS at best buy.. Hmmm let me take a look online real quick.

This one should work

http://www.bestbuy.com/site/APC+-+1500VA+Battery+Back-Up+System+-+Black/9307831.p?id=1218081367518&skuId=9307831&st=ups&cp=1&lp=5

Not sure what your budget is?

But it does have AVR, 5 UPS outlets, 5 just surge. And even should be able to run your cable "coax" connection through it. And has lots of battery runtime, etc. Its a bit on the pricy side for home $200 but not sure what your budget was or how much VA you wanted/needed.

edit: I currently have a cyberpower one that am happy with, if I was going to get a new UPS prob just get the new version of the one I have which is this one.

http://www.newegg.com/Product/Product.aspx?Item=N82E16842102070

And its like $50 cheaper.

[Roger H. Veteran]

I wouldn't keep your mac address up there.. people can clone that and activate their modem from yours

I see this all the time, people blocking out their MAC address on their router's info page and their wifi SSID name. Like what the hell could I do with that? Even if I knew where you lived, so i know your SSID and your MAC address? Really? :blink: It's gone as far as to see people blocking their internal (i mean 192.x ) addresses in screenshots! I'm like seriously!!!! LOL

As Budman pointed out just before i could finish typing! :D - Even if I could clone your MAC address on your modem there's no way Comcast is gonna let me connect to the network anyways with you on there. If that was the case people would just buy cable modems at best buy and clone their buddies MAC and get FREE internetz!! :woot:! Maybe if you weren't online at the sametime but who actually shuts off their cable modems, isn't that the point of "always on" connections?

I removed it anyways since that's your wish but yeah, that's the last thing i'd worry about. In some cases even public IP address i wouldn't worry about as anyone who wants to find you wouldn't go by searching for your IP address, they'd just port scan the hell out of everything until they get a return then try and hack that one.

snipped

As to a good UPS at best buy.. Hmmm let me take a look online real quick.

This one should work

http://www.bestbuy.com/site/APC+-+1500VA+Battery+Back-Up+System+-+Black/9307831.p?id=1218081367518&skuId=9307831&st=ups&cp=1&lp=5

I had the 1000VA version of that and for my cable modem, Linksys E4200 router and my Home Server they pull 60watts total so it gives me 78Minutes of usage before they die. I have the home server set to go to sleep after 10mins while on battery (then hibernate after 1hr) though so then it jumps up to 300+ minutes which should last me a good long time. My laptop (obviously using the battery) can last just as long as the internet would so no point in keeping them on any futher if the power doesn't come back on.

So unless you need more runtime than that, the other one is cheaper, I think staples had a sale on it for $99.

[neufuse Veteran]

I wouldn't keep your mac address up there.. people can clone that and activate their modem from yours

yeah in the old days..... now there is so much security on a cable network its extremly hard to do... you'd have to be in the same head end, on the same node..... which is basically saying on the same block of town.... they monitor where cable modems try to register now, and if its not in the town that the sub is at it wont allow it unless you call in with the account number asking for it to work... at least comcast has this implemented right now, i'd assume others have followed

[+BudMan MVC]

^ well said ;) There is being careful and then there is going overboard. The one that bugs me the most is hiding private address ranges.. This makes it difficult to troubleshoot or respond or give advice sometimes since you can clearly spell out which box by IP or draw out their network for them with the specific IPs they are using to be sure they understand.

To be honest the SSID and or mac of your wireless router could be helpful in tracking down your location, and I don't have any problems with hiding that if your so inclined - I try not to post mine, since someone can just use a database to find your location if so inclined. Which from actual IP much much harder, oh sure they can get a region but its not like 24 where they show you what room of the house the IP is coming from ;)

I don't have a problem giving away my netblock for IP, but just good practice not to post actual public IP if you ask me.. But as pointed out, most likely it would not be an issue.

But like I was saying with wifi mac and SSID, it could be seen as a privacy concern.

example - notice the mac, and ssid -- simple query of database could show you pretty much exactly what house the or atleast really close to where that wifi network is.

Keep in mind that is going to be the MAC of your wireless radio on your wireless AP or router.. If lan mac not an issue, if router without wireless again not an issue. But if your wireless router normally the macs are only +1 of each other, ie radio, wan and lan are in sequence.. So if had your wan mac, would not be too hard to guess your wireless radio mac - and from that it could be possible to look you up -- if in the database and find your location. Some really good databases out there mind you..

[chevyordeath]

Thanks for the edit, SHoTTa35 - and thanks for the quick security lesson guys :D

As for the batter backup - I just got back from Best Buy with this:

http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=BR1000G

$120 at Best Buy... wasn't too bad.

Hopefully this fixes my issue with my modem resetting! I'll cross my fingers!

[Roger H. Veteran]

Thanks for the edit, SHoTTa35 - and thanks for the quick security lesson guys :D

As for the batter backup - I just got back from Best Buy with this:

http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=BR1000G

$120 at Best Buy... wasn't too bad.

Hopefully this fixes my issue with my modem resetting! I'll cross my fingers!

Yeah that's the one i got. You can see what to expect from my usage case above :)

It's freaking big also :D Just a FYI! I didn't realize it was so big till i took it out.

[+BudMan MVC]

Yeah prob work fine - now will that fix your issue?? From the front page they did not mention AVR, but took a look at the details and does have AVR

"Boost and Trim Automatic Voltage Regulation (AVR) "

So yeah if that enough VA for you -- should be good.

[neufuse Veteran]

Having a receive level at -6.0db is ok, the closer to 0db the better but between -10 and +10 is acceptable

your sending levels at 49.0 dbMv is fine also.... you generally want them no higher then 55 dbMv this is how loud the modem has to talk (or scream) to the fiber node for it to be heard... to loud and it will cause problems, too quiet and it will cause problems... but you are fine where you are...

now the big question is what is your SNR? it should preferably be around 35-40... a good SRN would be at least 37... if you have below 35 you might be having noise issues on your line... you can only see this for downstream (Receive) to see upstream you'd have to get that info from the head end

[+BudMan MVC]

All good info and such -- but I find it hard to believe that bad signal strength or even worst SNR on the planet should cause the modem to actually power cycle - which is what the OP has stated its doing.

"The modem actually resets, the lights turn off, then they flash back on one a time like you unplugged it and plugged it back in."

Something clearly wrong with the modem if anything to do with signal strength or SNR would cause it to actually power cycle.. Now sure I guess if REALLY HIGH signal could cause it - maybe?? But if they were seeing such high levels wouldn't everyone in his neighborhood be more than likely having issues with the signal as well?

Clearly sounds like some sort of power issue to me.. We should know soon enough he just picked up a UPS and since it has a metering and logging on it should show if there is line elec problems.

[Roger H. Veteran]

I think something like bad SNR - and therefore a T3 error in the log will cause the modem to reboot after 3 consecutive errors. The power light will disappear as well and do a full reboot as it tries to sync up again. This is why my first response to the thread was about signals and sync.

It could definitely be a power issue though for sure so either way, good stuff for the OP to go hunting down.

[+BudMan MVC]

have never ran into that - but the OP should be able to see that in his modem logs.. Someone did post the 192.168.100.1 address, which is a common modem web access IP to be able to look at the logs. Couldn't hurt to keep an eye on that to see if seeing such errors. But if lost sync before the point that the modem reboots because of it the user would have no internet access - what kind of time are you talking between 3 consecutive errors, I would think the device would try pretty hard before it reboots on its own because of sync loss or the thing could just continuously reboot itself - and I have lost sync for quite some (days) and don't recall ever seeing the modem reboot on its own.

[Davo]

I've been having similar problems so this is good to hear. In the past month or so, my modem would stay powered on but would seemingly reset as I could see the lights flashing one by one. I know I have shoddy electric in this apartment so if it continues, I'm going to try plugging the modem directly into the wall as opposed to a surge protector. I have more or less the same levels as him.

[+BudMan MVC]

Welll I would never suggest you plug your modem directly into the wall ;) Especially if you have known bad power -- I would suggest you pickup a decent UPS like the OP did.. We should hear back from him sometime soon if it fixed his issue.

[Roger H. Veteran]

Granted this isn't the authorative source but it's a good one:

http://bradyvolpe.com/docsis-101/docsis101_station-maintenance/

T3 and T4 Timeouts

I wanted to close this topic with a discussion on T3 and T4 timeouts as I have received many questions on ?what causes T3 and T4 timeouts?? Fundamentally, a T3 timeout occurs when the cable modem fails to receive a RNG-RSP from the CMTS within 200 msec (after sending a RNG-REQ). A T4 timeout occurs when a cable modem fails to receive a RNG-REQ transmit grant MAP from the CMTS within 35 sec on the downstream channel (after receiving the previous RNG-RSP). There are number of reasons that these could occur and I will list a couple below for each and help guide you the root cause, but understand this is not and exhaustive list.

AFAIK - The modem will send the req and if it gets no response it will do a T3 timeout in the logs, then it will then try again in 5 minutes (don't quote me on that number but something like that) and if not then another T3 is noted in the log. It will do this 3 times and after the 3rd it will reboot itself to try gaining sync. If you are "out of sync" you don't have internets also so you wouldn't be able to do anything until it gains sync.

Here's a log I found that shows the T3 timeouts happening from 10-20minutes so i guess it depends on when the last response was received or something.

http://forums.comcast.com/t5/Home-Networking-and-Router-Help/Cable-modem-reboots-several-times-an-hour/td-p/669291

here's another showing even less:

http://www.ooma.com/forums/viewtopic.php?f=9&t=11344&start=0#p79161

I prolly should just go to some main source to get the how often the requests are sent but i'm so drained right now, It's Hot! - Apparently....

[+BudMan MVC]

Great info - Thanks!!

But again from reading that it looks like you would have atleast a 10 minutes of it trying without sync before reboot, so no internet for 10 minutes - then the modem could reboot. Maybe that is what is happening to the OP, but thats not what it sounded like to me. Sounded more like out of the blue he was surfing along doing whatever it he was doing and then no internet, lookup and see his modem rebooting.

tester.br is that how it happens -- or do you not have any internet for a few minutes and then you notice the modem reboot?

Either way clearly great info Shotta35 - thanks again!

[chevyordeath]

No dice. The UPS did not help. Was still resetting. Tried a few more things, such as running the coax through the UPS - that didn't help.

Receive signal would hover around -8 and then jump to around -15 hit mid -15 and the modem would roll over - 3 times in 15 minutes. After reboot it would be around -7 and then start climbing again.

Receive Power Level

-15.7 dBmV

Transmit Power Level

51.0 dBmV

Receive Power Level

-15.6 dBmV

Transmit Power Level

50.5 dBmV

I decided to move my router and modem to the complete opposite end of my house (I've conveniently wired my whole house with CAT5 so I've got outlets in each room that go to my switch) where the tech's meter wasn't reporting any 'leakage'. So far so good. My signals have been hovering right around here for 10 minutes or so:

Receive Power Level

-6.6 dBmV

Transmit Power Level

49.0 dBmV

Now I just need to decide if I wan't to return the UPS or not... lol. I will report tomorrow on rather or not I've had any restarts since moving the router and modem.

[Roger H. Veteran]

The UPS will be a good investment anyways :) Hell with summer being hot you can expect some blackouts or brownouts and then you'd definitely wanna have a UPS!

At least we narrowed it down a bit, there is no way to get logs on that modem?

[chevyordeath]

I suppose you have a point there. Unfortunately not - the best I can do is get signal readings. So far no resets though. I've got my fingers crossed.