Simple Check For Virgin Media Users

SuperHub 

Log in > Advanced settings > Network Status > Check the RxPower is between -7 and +3.

If your running 100mb in upstream section it should be no higher than 43 in the TxPower.

Hope this helps if you do find it is to high you need a small filter added to cable in router. Some people will say -3 to 7 is optimum but virgin engineer only two weeks told me the opposite. If it is more than recommended + it will basically overload your router giving you the feeling you have been capped and seeing lots of lag or even dropping out of lobbies.