HomePlug powerline communications networks link individual computers or network segments via low-voltage power lines. The powerline medium is a harsh channel, since it varies in time and has a high attenuation. This makes difficult to communicate different devices in distant places in a building. A possible solution is the HomePlug repeater we propose in this paper. We show that it is impossible to develop a repeater at the physical layer, so we have developed it at Medium Access Control (MAC) level. Its main distinctive features are transparency (no planning is necessary) and availability (it is built from off-the-shelf hardware).