The fronthaul between the Central Office, hosting the BBU pool, and the different located RRUs in a C-RAN has been based mainly on dedicated fibre links or, more recently, on dedicated lightpaths over a fibre network. A more cost effective solution is to deploy the C-RAN fronthaul based on Ethernet technologies but such solutions must be carefully investigated due to the very demanding latency and jitter requirements imposed by constant bitrate protocols, such as CPRI. In this paper, we conduct a worst case performance analysis to determine the maximum coverage length between the Central Office and each RRU imposed by CPRI, when the C-RAN fronthaul is based on EPON networks or based on switched Ethernet networks.