These Diablo Cable crossover cables work with popular Cisco router models 2801, 2811, 2821, 3825, 3845, 3640, 2621, 1721 and many others. The 26-PIN Smart Serial cable is used to connect to Cisco WAN Interface Cards including HWIC-2T, WIC-2T and WIC-2A/S. This DTE Male to DCE Male Smart Serial Crossover Cable will connect two WIC-2T, WIC-2A/S, HWIC-2T, and HWIC-2AS WAN Interface cards together in back-to-back fashion. Build back-to-back router connections, CCIE lab setups and frame relay simluations with the right cable and a manageable length.