Satellite links are very sensitive to their environments, and often become unstable. Operators have to monitor satellite links continuously in order to effectively determine their status. However, monitoring satellite links over a widely spread network demands great expenditures of time, finance, and human resources. The difference in skill levels among operators is also problematic. This paper describes a system for monitoring the status of satellite links on the Internet: Modem Watch Dog (MWD). MWD collects the status information of satellite links continuously, and visualizes the information on its Web. MWD provides easy access and understanding of the continuous state of satellite links for operators, even if they are not familiar with the operation of satellite links. MWD has been operating in the AB network. MWD visualizes the continuous status of a satellite link, and indicates the link's normal status and predicted problems caused by equinox Sun interference in Southeast Asia. Through the use of MWD, monitoring the status of satellite links can be easily accepted as part of the layered network operation of the Internet. © 2003 IEEE.