European shares traded flat on Tuesday, held back by Vodafone, after the world's second-largest mobile network operator reported huge impairment costs, Reuters reported. Vodafone shed 4.1 percent, making it the biggest faller on the FTSEurofirst 300, after it recorded 6.6 billion pounds ($11 billion) in impairments due to fierce competition and regulatory changes in Europe. At 1104 GMT, the FTSEurofirst 300 index, which last week hit a six-year high of 1,372.81, was flat at 1,358.58 points. The STOXX Europe 600 is trading on a 12-month forward price/earning ratio of 14.3 times, against its 10-year average of 11.8 times, Thomson Reuters Datastream shows.