How to Install a DSL Line From Demarc


The demarcation point (demarc) box is the point where your telephone company's wiring ends and your wiring begins. The demarc box is typically on the exterior of your home in a weatherproof box. The demarc box allows you to temporarily disconnect your wiring from the telephone company's wiring to troubleshoot line problems or add additional wiring. Choosing to wire your home from the demarc box will allow you to add a low-pass filter for your entire house and add DSL cable to additional rooms.

Things You'll Need

  • Tape measure
  • Drill
  • Ethernet cable
  • Ethernet jacks
  • Wire cutter and stripper
  • Needle-nose pliers
  • DSL filters
  • DSL modem
  • Measure the route of the wiring from the demarc box to the room where the DSL modem is located. Use the measurement to determine the length of Cat 5 cable required for the distance. Add an additional 3 to 4 feet of cable to provide for connections. Cut your Cat 5 cable to the desired length.

  • Drill a hole in the exterior wall above the demarc box where the new cables will enter the house. Drill a hole in the interior room where the Ethernet cable will come in for the DSL modem.

  • Run the Ethernet cable from the demarc box through the walls to the room where the DSL modem is located. If you don't want to go into the wall, secure the Ethernet cable to the baseboards.

  • Install the RJ-11 jack at the DSL modem's location. This jack will be used to run a cable directly to the DSL modem.

  • Open the demarc box to expose the customer hookup area. Feed your CAT5e or CAT6 cable into the bottom opening, creating a small drip loop directly under it.

  • Trim your CAT5e/CAT6 cable to make connections inside your demarc box. This will require you to strip away the Ethernet cable's insulation to expose the inner conductors.

  • Connect the green pair of twisted conductors to the demarc's green screw terminal. Check all the connections in the demarc box and close the panel.

  • Install DSL filters on each phone and fax machine that uses your phone line. Do not install a filter on your DSL modem.

  • Plug in the phone line to your DSL modem. Turn the modem on and make sure the DSL and Internet lights turn green before using the connection.

Tips & Warnings

  • CAT5e Ethernet cable is commonly used on home networks; however, you can purchase CAT6 Ethernet cable if you plan to install a gigabit network.

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  • Photo Credit blue red cat5 network cables together image by willem169 from
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