To extend an existing Ethernet cable, you can follow these methods:

1. Ethernet Coupler (RJ45 Coupler)

What you need: An Ethernet coupler and an additional Ethernet cable.

How it works: An Ethernet coupler connects two Ethernet cables, allowing you to extend the length without any special tools.

Steps:

a. Plug one end of the existing Ethernet cable into one side of the coupler.

b. Plug one end of the additional Ethernet cable into the other side of the coupler.

c. Connect the other end of the second cable to your device or router.

2. Ethernet Extension Cable.

RJ45 Female to Female Ethernet Extension Cable is ideal for extending ethernet connection by connecting 2 short network cables. Never worry about the network cable is not long enough anymore.

3. Replace with a Longer Ethernet Cable

Sometimes it's easier to use a single, longer Ethernet cable instead of extending. You can find cables in various lengths, up to 100 meters for Cat5e/Cat6 cables.

4. Ethernet Wall Plate (Optional)

If you're routing cables through walls or over long distances, using a wall plate with Ethernet jacks can create a more permanent and clean-looking solution.

Steps:

a. Connect the first cable to the wall plate on one side.

b. On the other side of the wall, connect another cable to the second wall plate.

5. Ethernet Switch

What you need: An Ethernet switch and a short additional Ethernet cable.

How it works: If you have multiple devices to connect or need to extend the cable length, you can use a switch as a repeater.

Steps:

a. Connect the existing cable to the switch.

b. Use another Ethernet cable to connect the switch to your device or router.

Each method should work well depending on your needs, budget, and available space.