Broadband (Cable, DSL, Satellite, Fiber Optics)/Intermittent web connectivity


QUESTION: My housemate and I each have a Windows desktop computer connected via ethernet cable to the same router receiving DSL from Verizon. The only difference between them is that his is near the router and mine is in another room. My internet connection (unlike his) has become progressively unreliable --after working very well for some two weeks--and at this point I can't access the web at all (this is being sent from a public computer). Other puzzling data: Windows indicates the connection is working, and repairing it has no effect. Even stranger: over the past weekend, my internet access returned to complete reliability for two days, only to fail again at 9:30 this morning. And none of these symptoms affects the other computer connected to the same router. What on earth is going on???

ANSWER: When you say Internet Connection are we talking both web and email or just web?

If web then I would guess the problem is something on your machine that is affecting your web browser.  Try running Internet Explorer with all add-ins disabled if that works you have a bad add-in.  I would also download and install malwarebytes antimalware, and install Microsoft Security Essentials which works a lot better than Norton antivirus.

Another thing people overlook in a browser issue is Flash.  Try uninstalling Flash from add remove programs and reinstalling.  And also download and install Google Chrome and see if that works better.

If it's both web and email then you could have an intercept robot program on your PC.  These get on there and intercept all web and mail and scan it for marketing data which they upload to servers.  Norton Power Erase can sometimes delete those, as can Avira Rescue CD.

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QUESTION: It definitely affects both web and e-mail. My internet access returned at 12:30 this morning, so I've installed Malwarebytes and Advanced System Care to hunt for bots (none detected so far). Tech support at Verizon (my DSL provider) tried to pin the problem on my ethernet cable - but that has no settings or moving parts, so how could it be working now but not yesterday?? I like your evil bot theory. . . Could that explain the intermittent nature of the problem? It only works during business hours?

ANSWER: Check the IP address that your PC is getting.  It should be a "private" IP from the range 192.168.x.x or 172.16.x.x or 10.x.x.x   If it is not it may be that your DSL modem is in "bridged" mode and you and your roommate are actually being handed "public" IP addresses.  If that is the case Verizon generally is going to restrict a residential DSL line to a single public IP number.  To see the IP double click on the Ethernet adapter icon and click support then details (for windows)

If your DSL modem is in bridged mode then it may be possible to put it into "address translation" mode.  What is the make and exact model number of your DSL modem?  If it is a bridged-only DSL modem then you can buy a router for it.

It is possible for a poorly made Ethernet cable to cause problems.  If your cable was purchased with the ends crimped on it then it's probably fine.  Inspect the ends, usually what happens is the cable gets pulled on and the insulation gets pulled out from the plastic plug, and then just the wires are holding the plug on the cable.  But if both ends of the cable look good and the plastic cable jacket is under the crimp wedge in the plugs, then I very much doubt it is the cable.  With one exception, if you have animals.  Cats will sometimes bite down on an Ethernet cable and their sharp little teeth will puncture right down in there and short things out then it is hard to see the punctures in the cable.  Rodents like pet rats love chewing the cables.  And of course, make sure that the cable says CAT-5 or CAT-5e or CAT-6 on it, if it does not say any of those then it's not category rated and will have trouble.  A few other cable issues are minimum bend radius on Ethernet is 1 inch, right angles are not allowed, meaning don't crush it in a door.  I had one once where the user shoved the cable down under the baseboard and it was punctured in several places by the upside down nail strips used to hold down the edges of wall-to-wall carpeting.  Another no-no are the paper insulated staples used for stapling zip-cord to the wall.  If you have to nail down Ethernet cable then use the plastic hooks with a straight nail in them, otherwise you interfere with the signal.

It is possible for the Ethernet chip in your computer to not properly negotiate with the Ethernet chip in the modem.  We see that more with iffy cabling though.  Once more, that is unlikely.

The evil bot theory would be based on the idea that the mothership server that the bot is reporting to might have crashed or gone offline.  But it would be a very poorly written bot that would block traffic while it's host mothership server was down.  Usually the people that write bots take a lot of care to write them so that they don't cause trouble because they don't want the users looking for them and uninstalling them.

Go through your control panel, installed software and uninstall anything on your machine that says "toolbar"

Look at the rest of the installed software.  If you don't recognize any of the titles, Google for their names.  I have seen many of these marketing programs use very short, undescriptive names so that people don't uninstall them when they are trying to speed up their PCs

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QUESTION: The modem is apparently providing the proper IP address, at least according to the Windows support details:

Physical Address: 00-0D-87-78-A9-9C
IP Address:
Subnet Mask:
Default Gateway:
DHCP Server:
Lease Obtained: 7/25/2013 10:35:00 AM
Lease Expires: 8/1/2013 10:35:00 AM
DNS Server:
WINS Server:

Of course, it also says: "Windows did not detect any problem with this connection..." so I wonder if the above info is any more accurate than a typical Windows error message. There is no indication on the modem/router (Actiontec model GT784WNV) that it can be switched between bridged mode and address translation mode.

Meanwhile, the cable is new CAT-6 with factory-installed connectors in excellent condition. It loosely follows the walls with no sharp corners and isn't nailed down. There are no cats, rats or other critters to munch on it - only a large dog who presumably keeps such activities to a minimum. Tangentially, a friend once told me that laying a second, unconnected length of cable alongside the active one somehow increases the speed of an internet connection. I've never tried it, but he did and believed he detected an improvement. Huh?

I've also uninstalled one toolbar and some miscellaneous unused programs, but nothing I didn't recognize. Of course, malware could still exist anywhere, but neither Advanced System Care nor Malwarebytes has found anything - and I'm STILL experiencing intermittent connectivity problems, sometimes for hours on end. Access will often return for less than five minutes and cut off again, as I scramble to read messages and do other things online. However--and this my be a clue--I've never had it cut off while streaming audio, watching a webcast or downloading a file. Somehow, the constant stream of activity seems to give the connection more tenacity. I wonder what that means. . .

That would indicate a negotiation issue with the Ethernet chip in the computer and the Ethernet chip in the DSL modem.  Maybe your side is in full duplex and the other side is in half duplex or something like that.  I would also bet your PC is a gigabit interface and the modem interface is 10/100.  Actiontec modems are garbage grade and many manufacturers - particularly Dell - use really cheesy gigabit Ethernet chips in them that have problems dropping speed to 100base T.

You can try buying a 4 port gigabit Ethernet switch and inserting it in between your PC and the modem.  That would be the best option if it works and most likely it would work.  Or you can try hard-coding speed and duplex on the Ethernet interface on your PC.  Or you can stick a USB wireless dongle on your PC and try associating to the modem and abandon the Ethernet cable.

What is happening is that DHCP traffic - which is based on UDP - it failing across the link.  I will leave you to Google the differences between TCP and UDP traffic and merely say that UDP is a lot more sensitive to this kind of problem.  The reason why streaming traffic helps is because the arp cache in the router isn't used during streaming.  In other words the router DHCP server has wiped out the entry for your PC since it has expired and it has not got confirmation from your PC that it's renewed the address.  Once the stream stops the arp entry times out and that's that until the next DHCP request from your PC.  ARP is also dependent on UDP.  Repairing in Windows isn't working because the hardware issue is trashing the DHCP request packets most of the time.

You can also try hard-coding the IP addressing in your PC.  Set the IP to or something high up like that.  That would be a hack.

Broadband (Cable, DSL, Satellite, Fiber Optics)

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Ted Mittelstaedt


I will answer questions on the following kinds of High Speed Internet connectivity; ISDN, Frame Relay, dedicated T1, higher speeeds such as DS3/OC3, wireless such as 802.11 and DSL. No questions on dialup V90 or Cable access. I can also answer questions on many types of Cisco routers, and a number of other brands of business routers as well.


I am the technical manager of Internet Partners Inc. an ISP.

I've written a book titled "The FreeBSD Corporate Networker's Guide" published by Addison Wesley

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