4

I am terminating my contract with my old ISP, however, because I've already paid my account till the end of the month, this connection is still active. I have also signed up with a new ISP who mailed me with a new modem preconfigured with all the settings necessary to connect.

After I hooked up the new modem, it negotiates the PPP successfully, but fails at user/pass authentication. I called up the new ISP and was informed that they couldn't even see my modem's attempts to connect, which led me to think that the new modem is somehow still trying to connect to my old ISP. The call was logged as a fault, but I'd like to be a little more informed on the problem myself.

How does a modem know which ISP to connect to? Is there a setting on it that uniquely identifies each ISP? Or is there something that needs to be done on the DSL/POTS cabinet down the road?

Improve this question
1
  • 2
    I'm pretty sure it has to be configured at the DSLAM in the central office. Your modem doesn't know how to do this. The "DSL/POTS cabinet down the road" is not involved. ADSL is a point-to-point connection. The opposite end from your modem is the DSLAM.
    – sawdust
    Commented Apr 13, 2013 at 0:12

2 Answers 2

Reset to default
4

It is up to your phone company to patch your line to the new ISP's DSLAM. When you signed up with the new ISP - they placed the transfer order with your local phone company and the phone company scheduled a date when the switch would happen. Your new ISP should be able to look up the date for you. The delivery of the new modem may happen before the switch - it does not mean that it would work right away. If the switch date already passed then your new ISP should open a ticket with the phone company. Otherwise you should just wait for the date.

Improve this answer
3
  • The switch had already occurred, however, it seems that they hooked me up to the wrong phone number (xxx-2050 instead of xxx-2048, which is the number I had from my old ISP). Could this have caused the problem?
    – deutschZuid
    Commented Apr 14, 2013 at 23:44
  • Yes. If they'd ported the wrong phone number, then that line -- the wrong number -- and not yours would have been connected to their DSLAM. To fix it someone had to go cross-connect your number instead.
    – goblinbox
    Commented Aug 27, 2015 at 22:38
  • @Alex P. - If the phone company has connected the circuit/line to the ISP, how does the modem negotiate a connection?
    – Motivated
    Commented Feb 15, 2019 at 15:58
0

How does a modem know which ISP to connect to?

It doesn't. It just tries to connect to any DSLAM on the circuit. Your circuit has to be physically connected to the correct ISP at and by the telephone company itself.

If you switched ISPs and the new ISP could not see your modem attempting to authenticate, it meant that the cross-connect hadn't been done yet (and your traffic was still going to the old ISP, with which the new modem would not work). The old modem will work until the cross-connect is completed by the telco or the month ends, whichever comes first.

Third party cross-connect order dates are very frequently missed. Best service happens mainly when you're switching to the telco's own or preferred ISP.

Improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .