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I understand that older DSL modems aren't compatible with newer technology, but is the case same the other way around? I.e.:

  • Is VDSL2 modem compatible with a VDSL connection? What about with ADSL or ADSL2 line?
  • Is VDSL modem compatible with an ADSL/2 connection?
  • Is ADSL2 modem compatible with an ADSL connection?
  • Or could it be so that *2 modems are downwards compatible only with *2 connections (this is just guessing...)

Or is there other logic? Or are they all just incompatible?

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I'm not sure, but you're probably being too general - while every (ADSL2+) modem I've used has been able to choose an older mode automatically (or manually), it's probably firmware/hardware specific: even if all hardware is able to do this, firmware may have technical or even intentional (locking) restrictions against it. –  Bob Feb 25 '12 at 8:55

2 Answers 2

up vote 12 down vote accepted
+100

VDSL is not compatible in any way with ADSL.

VDSL2 capable line cards (the ISP end) are compatible with ADSL2+ ADSL2 and ADSL - so you can use these modems on a VSDL2+ connection - Its easier to find on this juniper networks document, as well as this broadbad-forum presentation - i am unclear if its possible to use a VDSL2 modem with an ADSL connection

ADSL 2+ should work with ADSL2 and ADSL in both situations

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Actually there are modems that are both ADSL2+ and VDSL2+ capable, such as the Actiontec Q1000 or the Actiontec C1000A. The Actiontec Pk5000 originally was only ADSL2+ capable, but the current Actiontec PK5000 modems are now both ADSL2+ and VDSL2+ capable and Actiontec is working on an update to make their older P5000 modems also VDSL2+ capable.

ADSL2+ technology generally has speed capabilities of up to 20M downstream/896k upstream. VDSL2+ is newer technology and has speed capabilities far greater, such as 40M downstream and upstream speeds of 5M, 10M or faster, instead of the standard 896k speed. In some areas - generally major cities - there are now VDSL2+ speeds of up to 100M downstream/40M upstream available.

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