I just moved into an older house and the NBN guy told me the phone socket's been cut off and plastered over. I checked with the previous owner and he said that the cord is just cut off, sitting under the house.

I have a Cat 6 wall socket, and my question is:

Is it possible to connect the old RJ11 phone cable to the Cat 6 wall socket?

I want to use a Cat 6 plug just because there's no hardware stores nearby that sell the other ones. I intend to plug my FTTN (fiber to the node) modem into it.

  • 1
    When you say “modem” I assume you mean DSL modem and such, correct? May 10, 2020 at 19:00
  • Yeah, for FTTN.
    – Bananawon
    May 10, 2020 at 19:03
  • 2
    For fiber-to-the-node?! No. Hard No. Revising my answer accordingly.
    – Allen J
    May 10, 2020 at 19:08
  • apparently "NBN" is National Broadband Network, Australia's fiber project.
    – tedder42
    May 11, 2020 at 11:10
  • 1
    What is the wall socket connected to? Where does the old phone cable arrive at? "Under the house" is quite unclear for me. Basically, you really just need to extend the cable from where it is to where you want it. If you already have a Cat6 cable running from the current end of the phone cable to where you want to use it, you can most definitely just patch the together (using the appropriate tools, though, in order to avoid all sorts of interference and signal loss).
    – jcaron
    May 11, 2020 at 15:39

6 Answers 6


No. Both technically and politically.

The technical problem is that the "NBN guy" visited your premises to install a new cable between the node and your house and to install a new socket inside your house. This is usually done by tying the new cable onto the old cable in the street, then pulling the old cable out from the wall socket until the new cable appears inside the house. With the old cable cut at an unknown location it cannot be used to pull the new cable.

The political problem is that you do not have a first socket. It sounds as though it was removed illegally, or you would have been in the Telstra database as having no existing connection. Now that the installer has completed a job report on the unsuccessful installation, you are in the NBN database as having no existing connection, and are very likely to be classified as requiring a new installation not a transfer from POTS to NBN. Which is a whole different (and likely much slower) process.

Your question actually appears to be asking whether you can run VDSL over Cat3. Technically the answer is yes if you want a kilobit per second data connection. Politically the answer is no, as you will then have an illegal connection.

  • 3
    Ah... the vagaries of telephony and electricity down under.
    – Allen J
    May 11, 2020 at 21:28

It's possible. Quoting Steve DeRose, "in a pinch you can use 2 spare pairs in a phone wire to run a 10MB Ethernet connection (or possibly higher speed if your cable is better than typical CAT3 phone wire)." Here's a video on how to arrange the pins. The speed you get after auto-negotiation will likely disappoint.

In your comment you indicate this would be for connecting upstream to fiber for which Cat3 is woefully inadequate due to lack of wires and shielding.

  • 6
    It’s possible I’ve misunderstood something, but your answer seems to be addressing the reverse of what OP is asking. If I understand correctly, his broadband will be delivered to the house from the local cabinet over the existing PSTN cabling using something like VDSL. This is what’s cut off and under the house, and they want to terminate that into an RJ45 socket instead of an RJ11. So they want to use cat6 instead of what would be cat3 for the short run to the DSL modem, not vice versa.
    – Darren
    May 11, 2020 at 5:30
  • 1
    How they will deal with the physical incompatibility if they don’t have an RJ11 plug at the moment end is a different story.
    – Darren
    May 11, 2020 at 5:30
  • 2
    He says "RJ11 phone cable", so I addressed that. But you are right. OP is ambiguous at best.
    – Allen J
    May 11, 2020 at 13:07
  • yes, the RJ11 coming into the house I think, which would be transporting his VDSL down to the fibre node. A common misconception is that RJ11 is a cable type rather than a particular pin-out of a particular plug/socket.
    – Darren
    May 11, 2020 at 13:19
  • 1
    2 pairs would be capable of 100 Mbit if it were cat5 or better, but the cat3 cable is probably the limiting factor. The shorter the run, the higher the chance of success.
    – Criggie
    May 11, 2020 at 20:22

Id like to clarify a few terms here:

  • FTTN is Fiber to the Node. On the Australian NBN network this is then VDSL from the house to the node
  • Your connector may be marked as Cat6 but it's actually 8P8C
  • yes, 8P8C can be used to connect a POTS cable to

You will need to make sure you use the punch down spots on the back of your socket, and an RJ11 phone cable might be "wobbly" inside the socket unless you have an appropriate insert for the socket. But you can do it, and in fact this is done fairly commonly in commercial patch panels and installations.

  • ... and Fiber is Fibre ;-)
    – mcalex
    May 12, 2020 at 7:35
  • Fiber is preferred in American spelling; fibre is the preferred spelling in British English. May 12, 2020 at 12:11

Yes for an improvised RJ11 connection but a solid no for an RJ45 connection.

An RJ45 connection requires 8 wires while an RJ11 connection requires 4 wires.

I mean you can technically wire it up for RJ11 purposes as long as you match the pinouts on both ends of the connector. So it can be used as a janky way of getting an RJ11 connection using existing wiring.

While something like that would be useful for POTS (plain old telephone service) and/or a DSL (digital subscriber line) connection, it’s not useful for things like FTTN (fiber to the node) which you clarify in your comments that you wish to use it for.

And past that, it wouldn’t be useful for everyday/common ethernet networking purposes anyway; just POTS and/or DSL.

  • 5
    This is the only answer so far that seems to correctly understand the question. But isn’t FTTN delivered from the cabinet to the house over something like VDSL, making what the OP proposes possible?
    – Darren
    May 11, 2020 at 5:34
  • FTTN means that the connection is DSL (probably VDSL2).
    – jcaron
    May 11, 2020 at 15:33
  • 1
    It is actually possible to run two RJ11 lines (4 wires) off a single RJ45 wire (8 wires), so long as you're careful about matching the pinouts on both ends. But I don't believe this is what the OP was asking for. May 11, 2020 at 19:21

The short (and long) answer is NO.

POTS was always run a single cable (4 thin wires, not twisted) so cable aggregation is not possible. Cat6 cable 4 twisted pairs of thick wires in a single shielded cable - twist/shielding to get Cat6 speeds.

The best use of the POTS wire for you could well be as a "fishing" wire to thread a Cat6 Ethernet cable through the house. Otherwise just run new Cat6 cable; it in most cases cheaper than you think and in almost all cases cheaper than trying to "re-use" the old wires.


Yes you can and I don't know why the top answer argues no. I made an account just to comment on this.

I had a similar situation this year when I moved into an old Queensland cottage. The lead in from the street was wound up under the house and there was no socket in the house - at some point in time it had been removed.

As the other answers by Mark Henderson and Jake Gould say, just punch the right cables from the lead in into an 8P8C socket. You can purchase an adapter to go from 8P8C down from Altronics (search P1502 Modular Reducer 8P8C - 6P4C). This goes into the wall plate and will let you use RJ11 cable (phone cable) in the RJ45 (ethernet cable) socket.

This will not negatively affect your speeds, I get 94 down/36 up an 6ms ping over wifi with a similar setup (lead in from street to 8P8C plate >> adapter above to NBN modem >> NBN modem to router). This is FTTC.

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