Connecting keeps dropping, IP address going to 169.
 

Hi.

I have been using ntl Hi-Speed Broadband internet ever since it was introduced. I am using a 3Com Cable Modem (recommended by NTL at the time) to connect to the broadband line, and my computer is connected to that via Ethernet using a crossover cable.

I have had pretty sporadic service from it over the last five or six years - when it works it is great, but sometimes it just stops working for no apparent reason.

Recently this has got worse, and over the last two weeks the connection to the internet keeps dropping multiple times a day. It often reconnects after a few minutes, or if I reset the modem, but I cannot figure out why this is happening or how I can fix it.

Usually, when everything is running fine, I get an IP address by the DHCP server in the range 81.x.x.x and things work great.

However I will be surfing normally when suddenly, everything grinds to a halt and no more data will be received. Usually, I go and check the network settings, which still show the 81.x.x.x IP address but after a few seconds this changes to a 169.x.x.x self assigned IP address.

After a few minutes, or if I force the modem to reset (switch off for 10 seconds, etc) the IP addresss will usually flip back to the same 81.x.x.x IP address as before.

I believe my internet settings are correct, and that NTL's service is to blame. Indeed some of their engineers have told me that the signal-to-noise ratio in my area is abnormally high, and this could be the cause of the problem.

HOWEVER yesterday an NTL tech support person told me that as I am getting a 169.x.x.x IP address when the problem occurs, this indicates the problem is with either my computer or modem, arguing that the 169 self assigned address appears because my computer cannot communicate with the modem (and that if it could, but NTL's service was down, I'd get a 192.x.x.x IP address).

I don't accept this, I think that when my computer is unable to communicate with NTL's DHCP server because of an NTL connection problem, the computer is reverting to a self-assigned IP address.

Who is right? I have never seen a 192.x.x.x address as I can recall, and I see loads of other people on here complaining about problems similar to my own, which makes me doubt that my modem or computer are causing intermittent internet connection problems.

Even though I get a 169.x.x.x IP address when these problems occur, could this be NTL's fault?

Thanks for your help. Lastly I am running a standard installation of Mac OS X 10.3 Panther, I know I'm a Mac-head but I think that the problems I'm having are not related to my OS but to the connection I'm getting from NTL.

OH and also they always have messages on their answerphone about problems in the GU14 area, well I'm in the GU15 area so wonder whether my difficulties could be related.

Thanks for your help


Floop

Re: Connecting keeps dropping, IP address going to 169.
 

Hi Floop1977 and a great big huge :welcome: to the site m8 :)

Are you using a firewall on the computer ?

Do any of the cable modem lights chnage when you loose the connection ?

Re: Connecting keeps dropping, IP address going to 169.
 

If it was a problem with the computer and DHCP then you would get a 192.*.*.* IP address. If, when you unscrew the CATV the IP address stays on 169 after a full reboot then....

The NTL tech is right on this occassion.

There is something on the PC. As to what, answers Stu's questions and we'll see if we can help :)

Re: Connecting keeps dropping, IP address going to 169.
 

Thanks to you both. I've heard about this site (or the one that existed before NTL bought it, then closed it) but only just realised that it could actually be a useful resource for me, irritated as I am with NTL's shoddy service!

Okay. I am *not* using a Firewall with the computer. Mac OS X has one built-in but it is not turned on currently.

Regarding lights on the modem, this is what the front of my modem looks like:

Cable Modem Power / Cable Modem Status / PC Link Status / PC Link Activity / Cable Activity / FCN

When everything is working fine, the cable modem power and status lights are steady green, the PC Link status light is green to show there is a working ethernet connection between the modem and computer, and the PC Link Activity and Cable Activity lights blink orange as data is passed from the cable modem to the computer.

When things go wrong and I get the 169.x.x.x IP address, usually the cable modem status light blinks orange repeatedly. In my mind, this suggests that the cable modem is having difficulty handshaking/maintaining a connection with NTLs servers.

I just did a test in case it provides useful information. My connection was working fine, and then I unplugged the CATV wire from the back of the cable modem and watched what happened. The Cable Modem Status light started blinking green, then blinking orange, then my computer's IP address changed to 169.x.x.x .

After a few minutes, I plugged the CATV wire back into the cable modem, and the cable modem status light started blinking green, then went to a steady green. However my IP address remained at 169.x.x.x and so I unplugged the Ethernet line to my computer, watched the IP address go blank, then plugged the Ethernet line back into my computer, as I have heard this forces the computer to re-attempt getting an IP address.

Hey presto, my IP address went back to 81.x.x.x and everything is working again.

However at no time did I get a 192.x.x.x address so not quite sure what this means. Could it be because I am running Mac OS X - perhaps my OS always self assigns a 169.x.x.x address when it cannot find anything else (maybe 192.x.x.x only appears on Windows systems - hmmm).

Your help and or suggestions are greatly appreciated!



Floop

Re: Connecting keeps dropping, IP address going to 169.
 

When you get the 169 ip address what happens if you try this -

Goto the Apple/Menu/Sys/Pref
Choose network.
Drop the pull down and select port config
Choose the ethernet adaptor
Take the tick from the check box of the port.
Then Apply Now.
Then retick it.
Then apply now.
Close Sys/Pref.

Does that renew the IP Address, if so not ideal but its quicker than unplugging and restarting.

You will have to bear with me here on the above as my own Mac is currently sick and in for repairs :(

And also from memory as an ex tech i think the light sequence you are getting is the modem failing on the downstream.

I dont think the CMX 3 Com has an internal diagnostic page but maybe docs diag will work take a look here

:)

Re: Connecting keeps dropping, IP address going to 169.
 

Quite right: a blinking orange light can only be caused by an NTL cable signal problem, and cannot possibly be caused by any problem with your Mac. The NTL techie was wrong about the 192 address because I believe the 3Com modem does not support that feature. You should report this to NTL Tech Support as a problem with the NTL line, stressing the blinking orange LED and make sure they understand which model of modem you have (otherwise they might assume the Ambit).

Re: Connecting keeps dropping, IP address going to 169.
 

I have taken off the metal end of the cable in order to slide it under the partition wall. What this means is, I have bare copper running into the back of the modem. No problem, except when it slips out and if that happens I get a 169.*** like you describe above.

I just mention this as it sounds like yer cable is broken, very noisy or at least the transmitted connection sounds as if its intermitent.

I get my ip back by checking the cable, make sure the modem has got its link back, reboot it and then reboot my pc and the ip changes back to normal.

Re: Connecting keeps dropping, IP address going to 169.
 

rdhw is right, the 3com modem does not support assigning its own IP addresses in the 192.168.x.x range, the technician you spoke to probably wasn't aware of the 3com modems - there are only around 1000 of them left on the network - that's less than 0.001% of customers - so new techs aren't given a lot of information on them anymore; information on them is however available if you know where to look on the intranet!

I'd back up what other people are saying - seems like a cabling issue, or possibly the 3com has given up the ghost. Give TS another call next time you're getting a 169 IP (and before you reset the modem to get your IP back), and hopefully this time you'll get someone who knows more about the 3com modems.