IPv4 addresses have been depleted in February 2011, when the IANA allocated the remaining last five /8s IPv4 address blocks to the RIRs. IPv6 has been developed by the IETF as a solution to the exhaustion of IPv4 addresses. In this paper, the authors present some models to evaluate the performance of IPv4 and IPv6 in Ethernet networks, the most widely-installed local area network technology. Their models can be used for any variant of Ethernet technologies (10 Mbps, 100 Mbps, or 1000 Mbps). They introduce a lower-bound model for the one-way delay and an upper-bound model for the throughput, in both IPv4 and IPv6.