Computer network allows the sharing of data and resources in timely and an efficient manner. The devices used in computer network may be wired or wireless. Although wireless network provide more flexibility than wired network, but still to achieve fast data transfer speed most of the offices and colleges labs are still functioning on fixed infrastructure i.e. wired LANs. Wired LAN provides better results in terms of packet-loss and handover latency than wireless LANs. This paper simulates an office LAN using OPNET IT GURU EDUCATIONAL VERSION 14.5. Evaluation has been done onto different devices in different extended topologies, measuring performance metrics like traffic sent, traffic received, delay, packet loss that has occurred at lower levels of packet loss and collision in the Ethernet environment on different extended topologies. In addition, simulation shows the performance of extended LAN with respect to the utilization of hub and switch on mentioned parameters.