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Will ADSL router work on fibre line ?

starfry
Rising Star
Posts: 244
Thanks: 1
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Registered: 14-09-2007

Will ADSL router work on fibre line ?

I was wondering if my current ADSL router (a TG585v7) would still work after my line is upgraded to fibre. I realise it won't work at VDSL speeds because it lacks the required support but I wondered if it would work at all.

I'd like to upgrade but will need to migrate my network setup to the new router and wondered if I could use the existing one on the upgraded line until I do that. Also, it would allow my current router to serve as a backup in the event of a fault with my new router.

I've searched, but I cannot find an answer to this anywhere. My gut feeling is that it won't work but no harm in asking Smiley

4 REPLIES
RealAleMadrid
Pro
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Registered: 07-07-2009

Re: Will ADSL router work on fibre line ?

No, you must have a VDSL2 modem or combined modem/router.

bmc
Pro
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Registered: 28-02-2017

Re: Will ADSL router work on fibre line ?

I believe you could get an original OpenReach modem to use with your current router as a temporary solution (plenty available on e-bay). These are from the early days when the modem and router were not combined.

 

Then make the change at a time that's suitable to you.

 

Brian

Community Veteran
Posts: 6,277
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Registered: 30-07-2007

Re: Will ADSL router work on fibre line ?

I'm not sure the TG585v7 had a WAN port facility OOTB. Whilst it IS possible to reconfigure it to use a LAN port as a WAN port it's not trivial. Also would the TG585 have the oomph to handle a fibre line at anything like the max speed ?

starfry
Rising Star
Posts: 244
Thanks: 1
Fixes: 1
Registered: 14-09-2007

Re: Will ADSL router work on fibre line ?

I've been doing some reading and I tend to agree that an ADSL modem won't work with VDSL. However, I am struggling to understand WHY.

Having done some reading, what I've understood so far (and I might be wrong on all of this so please correct me if so!) is that the *DSL protocols all split the available bandwidth into "bins" or channels of 4.3215KHz and that each *DSL variant differs in the number of these that it uses and also how it uses them, the latter being a "band plan" defined by the standards as an *annex* or *profile*. Depending on line quality, a varying number of these channels will be suitable for use and the protocol sorts out what to use and what bit rate each can handle.

Understanding that leads me to believe that the *DSL variants should be broadly comaptible as long as the modems at each end of the connection (i.e in my router and in the DSLAM at the exchange/cabinet end) support the same band plans.

I expect that's where it falls down - the DSLAM in the FTTC cabinet only support the band plans required for VDSL2. I think the band plans for ADSL degrade (are backward compatible) but those used for FTTC VDSL dont.

When I realised that the copper pair back to the exchange is still used for voice, I also wondered if the ADSL signal might end up on that link but it won't because the cabinet DSLAM only passes the voice band onto the copper. I wonder if they bother disconnecting the copper from the ADSL DSLAM in the exchange after connecting FTTC.... It's all quite interesting, if complex, looking beyond the router and trying to understand it Smiley