What causes modem to change IP address

My IP address has changed and I now cannot log on to the Internet on my home PC , why did this change happen? I have tried renewing it but it won't renew an error message comes up telling me O must contact my service provider to find out what is wrong. I did that and they are sending me out a new modem but they never told me why it happened to begin with. How can an address just chafe witout anyone making it change? Did someone hack into my PC or what? Thank you for your responses I'll just read them and reply if need be.

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You get an IP address using DHCP, the D stands for 'Dynamic' and hence your IP changes. The speed you get from your provider is most likely sent to your modem using DHCP parameters/tftp too, and maybe your modem is no longer supported (did you get a free bandwidth upgrade or anything?) so your IP failed to renew to a valid IP. What is your new IP btw, if it starts with a 169.x.x.x it's given itself an IP using APIPA, 'cos it can't get one from your provider.

A while ago the performance of my cable modem dropped off horribly, 'cos it was no longer supported (without DHCP parameters, it reverted back to 512kb), I got a new modem, and BANG, I'm running at 9.5Mb.

 

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The other less likely but still possible explaination is that the ISP has moved to using the IPv6 format for it's modems. If the old modem only supported IPv4, then it would likely fail because it can't have an IPv6 address allocated.

 

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Was thinking the same thing. If it's a massive internet provider they might be moving to IPv6...internally. I would think NATing it externally would be some headache though. You sure can't spit out IPv6 to the whole internet just yet...

 

Indeed, it would be a very slow process. Obviously internal and done by the larger providers because it gives them the opportunity to lead the field.

 

Also, do you have a router between your modem and PC?

 

No, I do not.

The new IP addy starts with 169.

So I wait for the new modem and everthing should be alright then?

 

No, you'll have to resolve the reason why your PC can't obtain an IP from the ISP in the first place (which is why is has a 169.254.x.x address).

I doubt a new modem will fix it, unless the one you were using has died. Are you behind a home network (router)?

 

Do you connect to your modem via an Ethernet cable?
Maybe make sure your Ethernet card is enabled and there are no conflicts in device manager.
Make sure the cable is good too.
Also try powering off your modem for 5 minutes, and then power it back up.
I've seen that resolve odd issues like this before.

On your modem, are all the lights on? These is usually one labeled "on-line" or "DSL" that indicates your connection to the network.
There may also be one labeled “Ethernet” or similar that indicates your connection between the modem and PC.

 

Well , the new modem arrived and all is well once again. I guess the 3 year old one died and that was the only problem. I've set it up and now everything seems to be back to abnormal!:shrug:

Thanks once again for all of your input, I was using my cell phone to communicate until my new modem arrived to see if it would work.

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Yes... I guess...maybe not. Really the modem doesn't have anything to do with this problem unless they did it on purpose to phase out old modems.

You got an apipa address, which is almost totally useless. The ISPs DHCP server that hands out IPs cannot reach you or you can't reach it. However since apipa is "working" your modem is technically "good". It took a 169 address which all network devices will do if they can't get a DHCP address and will be able to communicated with other devices with a 169 address...which can be hard to do.

 

k I read the last message , dunno what the hell went wrong with your old one.

 

What nietzschefan sad. I would however ask your ISP why your old modem stopped working, or I should say, why they stopped it from working, because if it allocated itself an address using APIPA it's working fine, so I would guess they ceased support for your type of modem, and just sat back and waited for people to complain, rather that pre-emptively send out new kit.

As I work from home, and rely on my Internet connection, such behaviour from my ISP would be totally unacceptable. But then, I used to work for my ISP, and we were far too professional for that ...

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Well, I guess that my IP did do something but I cannot really do much about whatever they are doing so I just have to do as they suggest when I call them. They did send the new modem rather fast, 2 days and now all is back to abnormal once again. As you say they should have sent the new modem if they were going to switch the addy on anyone but they didn't. :shrug:

 

Could be that their TFTP malformed the firmware through trying to train the line. Obviously when the firmware went down they no longer had any control over re-flashing, so would send out a new one.

 

I do not know what that means so I can't answer your question.

 

APIPA is a Windows service that runs on the local machine, and has nothing to do with the modem. If you turn on a Windows machine with no LAN cable connected and no wireless NIC, it will obtain a 169.254.x.x IP address. The ISP probably did not do anything to make it stop working, as phlog suggests.

If the modem was 3 years old, it could have just died. Electronics fail, that's not news.

 

The IP would be allocated by the 'modem' in this case.

The 'modem' failed at the hardware level, it was hence no longer able to answer the RARP from the NIC in the PC. The PC failed out to 169.

The replacement 'modem' has a functioning hardware set so DHCP was back to normal.

 

So it happened again but this time I entered my addy MANUALLY Through the TCP/ IP setup instead of allowing for an automatic renew. That seems to be doing the job but it just bhappened again a few hours ago so I won't know for a day or two if it will hold.

 

Sounds like their DHCP server is fucked or the IP allocation is full. You are able to manually grab an IP and it works?? What ISP is this, Homer Simpson's?

Bet your next problem is an IP conflict.