Router dying after inactivity on network

[DazedAndConfused]

Hello,

I am running into a problem with my very basic at-home setup, and I am hoping someone could point me in the correct direction for fixing it.

Currently I am working with: a cable modem, Motorola SB6141, providing Comcast cable; my router, an Asus AC-66U in router mode; and an access point, an Asus AC-56U. When I restart everything and it boots up, it works perfectly; the access point has a static IP outside the DCHP range, I can access both the router and AP through their IP's, etc.

However, after a few hours of inactivity, the router stops accepting connections. Whenever this happens, I have to go down and manually restart the router; I also find at the same time that the modem is restarting. I'm not sure if its coincidence or if the modem is constantly restarting until I fix the problem.

The clients I am using are two iPads, an iPhone, and a Macbook pro. I have not yet had a chance to unpack any other wireless devices.

I did notice last night while attempting to fix it on my own, that the mac address of the laptop, after it went to sleep and was woken back up, would not accept the old IP address - in the log of the router, there were hundreds of lines of dhcpd_offer and dhcpd discover messages, but never the request or ack messages that the other clients would get when they successfully connected.

Is it possible that the laptop is flooding the router with so many connection attempts, the router is dying? Is there anything else someone could recommend as to the reason my router loses its connections on a regular basis?

thank you!

 

[stevech]

Did you say that only one laptop on WiFi is having an issue? Other wifi clients are OK? If so, this says the router isn't at fault?

Try with 2+ different WiFi clients to prove the client is not at fault.

 

[DazedAndConfused]

Hi Stevech,

Thanks. I have a difficult time determining which device is causing the problem - once the router disconnects, no wireless devices can access it, but that may just be due to a freeze caused by one client in particular.

It was suggested to me in another location that, due to the difficulty that the laptop is having re-connecting after receiving its original IP from the DHCP server, that I set it to a static IP and see if that helps. That may eliminate the laptop from the cause of the problem. If anyone has any other suggestions I would be very grateful, thank you!

 

[CaptainSTX]

Set a fixed WiFi channel. Leaving the setting as automatic on the router can confuse some clients.

 

[sfx2000]

Sounds like you have more than one DHCP server on the network...

 

[DazedAndConfused]

I've turned off the wifi network and plugged the laptop in directly. That does not seem to have fixed the problem. I've also done some looking around - it is possible that the modem is the problem, and not the router itself. The modem is a SB6141 that I purchased myself just a month or so ago, but I am using it on comcast's network and apparently there are some connectivity issues with that model modem.

The modem does restart quite often, after viewing its log, so I'm going to pursue that as well. I wonder - the SB6141 says that DHCP is enabled when the WAN access is lost, could that be causing my trouble, if the modem is losing its connection regularly?

 

[sfx2000]

I've turned off the wifi network and plugged the laptop in directly. That does not seem to have fixed the problem. I've also done some looking around - it is possible that the modem is the problem, and not the router itself. The modem is a SB6141 that I purchased myself just a month or so ago, but I am using it on comcast's network and apparently there are some connectivity issues with that model modem.

The modem does restart quite often, after viewing its log, so I'm going to pursue that as well. I wonder - the SB6141 says that DHCP is enabled when the WAN access is lost, could that be causing my trouble, if the modem is losing its connection regularly?

Sounds like the SB6141 is rebooting - check the info there for status, signal, and the logs - access the modem here -- http://192.168.100.1

You might have to call Comcast and work with them on their end - I know, painful perhaps, but if you get a good tech, it might be something simple and easy to fix.

 

[stevech]

I've turned off the wifi network and plugged the laptop in directly. That does not seem to have fixed the problem. I've also done some looking around - it is possible that the modem is the problem, and not the router itself. The modem is a SB6141 that I purchased myself just a month or so ago, but I am using it on comcast's network and apparently there are some connectivity issues with that model modem.

The modem does restart quite often, after viewing its log, so I'm going to pursue that as well. I wonder - the SB6141 says that DHCP is enabled when the WAN access is lost, could that be causing my trouble, if the modem is losing its connection regularly?

The cable modem should not restart frequently. Check the cable modem's cable system RF signal strengths:
From a PC,
http://192.168.100.1 no matter your subnet number.
You should see the modem's info pages. One page displays the downstream (ISP to you) signal strength in units of dBmV.
And
upstream (you to ISP) signal strength.

Downstream should be 0dBmV, +/- 6dB or so. Larger is better.
Upstream should be in the 40's or so. Smaller (lower) is better.

Look at this at various times of the day.
The upstream will vary widely. The upstream is how much power the modem is sending into the cable system to get to the "head-end". The head-end sends commands to the modem to adjust the upstream power so that the strength at the head-end is nearly the same for all customers.

The max upstream power the modem can produce is about 55dBmV. If your modem is in the 50's, and hits 55 or so, it is likely that the signal is too weak at the head-end. This will cause frequent rebooting due to loss of synch.

The upstream is also called the reverse signal as it goes to the cable system. Many TV set top boxes also send an upstream signal to the head-end - different frequency than the cable modem so they coexist. This TV upstream is for video-on-demand, box admin, switched digital video (SDV) and so on.

The usual cause of upstream signal too high/loss of lock (modem lights blink abnormaly, then it reboots) - include

Too many coax cable splitters in the line from the modem to the incoming service coax. Arrange for there to be just one two-way splitter for the line to the modem. First in the line.

Bad, missing, or incorrect type of cable amplifier for your home. Most amplify only the downstream and must have reverse (upstream) path, and some have amplified upstream as well for severe problems.

Loose connections at any splitter

Cheap splitters

damaged coax cables or flaky connectors - often very subtle. A tiny air-gap in the inner conductor of the coax often affects only upstream as it is at a much lower frequency than TV and cable modem downstream.

Unknown/illegal splitters hidden in walls that are in the path to the cable modem. In a condo, it could be a coax passing through a neighbor's attic where there's an unintended/illegal splitter.


So watch those cable modem signal levels.

 

[DazedAndConfused]

Thanks Stevech,

Temporarily I am going to be picking up another rental modem from Comcast and putting it into full bridge mode until I can get all the other parts of the network operational. I think there are too many moving pieces at the moment.

Over the weekend I was able to keep the network working flawlessly for 6 straight hours by streaming youtube constantly; however, within 15 minutes of the last video ending, it all fell apart and everything had to be restarted to retain its connections. I think the modem is losing its connection, and then something about that causes the router to freak out and then no one can connect to anything.

I did take a look at the levels yesterday morning and last night - all the downstream levels are ranging from 2-4dB and the upstream levels are 46 or 47, depending on the restart of the modem. I believe there are two splitters between the drop and the modem - one outside right at the drop, and one inside to split the TV and Modem. Honestly, I don't know what the outside one is; its a single-family, and we only have one TV and one Modem. Regardless, we seem to be getting acceptable levels in both directions, and those are fairly stable across all restarts.

 

[stevech]

But.. you said you see the cable modem rebooting frequently. Cure this before worrying about routers and WiFi.
keep an eye on the modem's lights and signal levels

 

[fistv]

But.. you said you see the cable modem rebooting frequently. Cure this before worrying about routers and WiFi.
keep an eye on the modem's lights and signal levels

Agree. my cable modem might reboot once a month and when it does my network comes right back up, my cable modem, router, switch and AP are all on a 1000kv UPS that will keep all of them up for over 24 hours so I don't loose my routers logs.

 

[DazedAndConfused]

Yes, that is the plan. With the comcast router I should be able to determine if it is a modem / line issue. Then they will be forced to fix it, rather than simply tell me that it is my equipment and they can't help me.

 

[fistv]

Thanks Stevech,


I did take a look at the levels yesterday morning and last night - all the downstream levels are ranging from 2-4dB and the upstream levels are 46 or 47, depending on the restart of the modem. I believe there are two splitters between the drop and the modem - one outside right at the drop, and one inside to split the TV and Modem. Honestly, I don't know what the outside one is; its a single-family, and we only have one TV and one Modem. Regardless, we seem to be getting acceptable levels in both directions, and those are fairly stable across all restarts.

I don't know whether this is part of it but the local cable tech put a new splitter, 3 way in as soon as it entered the house, the first connection goes to my cable modem, the rest go to other splitters to the other cable tuners and my replay5000. That was done when they ran a new cable from the street with a ditch witch, all underground utilities in my neighborhood. The old cable was from when we built the house in 85, it was replaced 4 years ago with a newer much heavier cable, three times as thick. Now if we could just get the township snow plow drivers to quit breaking the plastic cable maintenance tubes on the two corners when they plow snow we'd be all set. One comment the tech made was that those splitters do degrade over time.

 

[sfx2000]

Yes, that is the plan. With the comcast router I should be able to determine if it is a modem / line issue. Then they will be forced to fix it, rather than simply tell me that it is my equipment and they can't help me.

Good luck with it - reading back thru the thread - the SB6141 that you purchased - this a black housing or a white housing - the only retail devices are white, the black housing devices are carrier refurbs...

Current retail firmware on CoxHSI: SB_KOMODO-1.0.6.12-SCM00-NOSH

it's been stable enough - attached also is a screen shot of my signal stats...

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