Unreliable Cisco DPQ3925 Modem/Wi-Fi Router

Further Information.

The main issue here is that the Cisco Router (Wi-Fi _and_ ethernet) DHCP server is failing to renew IP addresses. About every 30 days, my Wi-Fi and ethernet connections to the internet fail.  I don't know if this is hardware or software, but I think I need a new Modem/Router.  The "fix" is to unplug and then plug in the Cisco device and let it reboot. Then, everything is back to normal (for a month, or so.....)

David

Further diagnosis has indicated that the problem is the DHCP server in the router - after about 30 days, it stops assigning IP addresses, and (all) internet connection fails.  This has now happened at least four times since the Cox router was installed late last summer.  It seems to be happening more often now.  I usually notice this on my iMac (which is connected via Wi-Fi), since I use that system most.  However, this time, it failed first on my PC which is connected via Ethernet.  I was mislead by the Windows messages saying no Ethernet cable was connected.  The cables are fine, and swapping known good cables didn't help.  I got two clues as to what was happening:  (1) Windows diagnostic tests gave me an error message that "no IP address was assigned"; and (2) connecting my Netgear N300 Wi-Fi router to the Ethernet wall port, and then running an Ethernet cable from the N300 to the PC restored my connection (Wi-Fi on the N300 was turned off).  What was happening was the N300 DHCP software was assigning the IP address (which is what the Cisco was supposed to do, but was not).

I pulled the power on the Cisco, restored power and it rebooted.  Everything is back to normal (except for my Solar Panel network connection).  

I don't know if it is the Cisco software or hardware causing this problem, but I am going to call Cox technical support and ask that someone come out and replace it.  Rebooting the router every month is not a reasonable solution.  (On previous failures, that is what Cox support would tell me to do - but I know this shouldn't be needed.)

David 

Is restarting your network once a month really a problem.  A router is just a dedicated computer, usually running a version of Linux and firewall software.  Don't you reboot your PC at least once a month.  Most smartphones require a reboot more frequently.  I normally take my network down for 5 min or so then restart every 2-4 weeks to clear everything out.

If it happens daily or even once or twice a week, now that's a problem.  I've know people who put their router on a lamp timer, the timer would restart the router in the middle of every night to keep it working.  But 4 times since late last summer??

BTW, sounds like a firmware issue, maybe a memory leak.  I've seen this type of issue with many routers ... had one which crashed at least once a week.  As soon as I replaced the factory firmware with dd-wrt, no more crashes.  There's another benefit of separate devices,  If you have a router giving problems and it will take open source firmware, you can just replace the firmware.

I think I am going to ask for a new Modem/Router.  As I mentioned, before the Cox Cisco router was installed (and my Netgear router removed), the Netgear N300 had run without problems, or need to reboot for three years.  I don't agree that rebooting the router on a regular basis should be necessary.

If someone can tell me how to update the firmware on the Cisco device, I can try that.  I looked for that setting a while ago and didn't see anything obvious.

I am nervous about having Cox swap out the device because I have SunPower sending someone out this week to figure out why installing the Home Security system knocked out the Solar monitoring ethernet connection.  The ethernet connection for the SunPower connection shows no internet.

David

I think that is what I saw when I looked at this a couple of months ago.  Maybe the firmware has become damaged and a reload will fix it.  How do I schedule that work?  Do I call Cox Internet support and ask them to do it?

David

I don't need to reboot to apply the firmware?  Everything seems the same here now - my Wi-Fi connections seem fine.

The real test will come in about 30 days to see if I have to reboot it again to fix the DHCP process.  I will repost then with the results.

Thanks for trying the firmware update.  I have a Sun Power tech coming tomorrow to see if he can figure out why I lost that ethernet connection.

David

Everything is working fine now.  I had a Sun Power service tech out to diagnose my lost ethernet connection to their solar panel monitoring system.  We had to replace one ethernet plug that connected to their monitoring system.  One wire pair was not connecting, and the new plug fixed this.  Normally, the Cox internet only needs two pairs - but now, it looks like all four wire pairs need to be functioning.  I wonder if the install of the home  security system (on March 23rd, which is when the Sun Power connection failed) now requires four-pair service.  It is very unlikely that the plug failed - something changed in the network configuration.

In the process of diagnosing this, we discovered that a switch in my wiring closet that linked to the downstairs ethernet ports in my home had been bypassed - so that I don't have ethernet downstairs.  My upstairs computer room ethernet is connected directly to the Cox Modem/Router - so that works.  I don't know why the switch was bypassed - this happened either when Cox installed TV service last summer, or when the Home security system was installed in March.  I don't really need the downstairs connection, but it is strange that this was disconnected.

The final test will come in a month or so - to see if I have to reboot the Cisco router.

David

10BaseT and 100BaseT (10 and 100Mbps) Ethernet only used 2 pair.  1000BaseT (gigabit) Ethernet requires all 4 pairs.  Did you switch from a 100BaseT device to gigabit at some point?

Nope!  The whole house is wired for megabit ethernet.  All I can figure is that the Cox Modem/router that was installed is requiring wiring that supports Gigabit (some configuration that is user adjustable?).  This whole thing is weird.

David

Your DPQ3925 should have gigabit ports.  Specs say 10/100/1000 auto-sense ports.

10/100 only require 2 pair but must be the correct 2 pair.  It uses the pair on pins 1&2 and the pair on 3&6, by standard the green and orange pairs.  I'm not sure if the 3925 will function in 10/100 mode if one of the other pairs is out but definitely won't work if pins 1,2,3 or 6 are out.  I have been doing Ethernet wiring for over 25 years, even back when 10BaseT was standard and 100BaseT a promise, we connected all 4 pairs.  So, as long as they used Cat-5e or above wire and was installed properly, your house should support gigabit Ethernet.

FYI, 568A standard wiring:
1 - white-green
2 - green
3 - white-orange
4 - blue*
5 - white-blue*
6 - orange
7 - white-brown*
8 - brown*

* not used for 10/100BaseT, required for 1000BaseT and above.

It was white-brown or brown that failed, I think, but I don't remember exactly what pair the Tech fixed.

If the Cisco is "auto sensing" port speed, why would it suddenly change from 100Mbps to 1000Mbps? I didn't think the Home Security install tech put in a new Cisco Modem - and that is the date the Sun Power connection failed - so something else happened.

I checked the cable in my wiring closet and it is 5e which I understand can support Gigabit ethernet.  (I was told that the house only supported 100Mbps, but I guess it do have more capacity.)  Right now, all my computers (except the PC) are connected via Wi-Fi, so ethernet speed is not immediately relevant.  I have the Cox 50Mbps internet connection, so I should have ample bandwidth.

David