Power dispatch depends on a reliable master station of a dispatching automation system. To assit with reliability, redundancy technologies have been widely adopted. In this paper, a test method of redundancy reliability for a Local Area Network (LAN) in the master station of a dispatching automation system is proposed. From test results with such as Network Interface Card (NIC) bonding, Virtual Router Redundancy Protocol (VRRP), and switch stacking, the reasonable ranges of key parameters such as the polling period of Address Resolution Protocol (ARP) and the preemption delay of VRRP are determined. The amplification effect of the Spanning Tree Protocol (STP) on network abnormality is revealed when the link is frequently interrupted. It is found that the status of standby NIC is difficult to monitor in real time under the main-standby mode of NIC bonding, and the abnormality of non-directly connected links cannot be detected in the load-balance mode of NIC bonding. After the switches are stacked, non-redundant potential fault points are added, and redundant Multi-Active Detection (MAD) can reduce the risk of stack splitting. Redundancy reliability recommendations for different network configurations are proposed to guide the design, construction, operation and maintenance of an LAN. This work is supported by the Science and Technology Project of State Grid Corporation of China (No. 5108- 202040024A-0-0-00).