Cisco offers a variety of connectivity, expansion and upgrade modules and cards to accommodate the customer specific needs. Cisco's components are easily and inexpensively upgradeable as customer requirements change.The PA-T3+ port adapters provide a full-duplex operation at T3 (45 Mbps) speed. The PA-T3+ supports both 16- and 32-bit cyclic redundancy checks (CRCs); the default is 16-bit CRCs. You can change the default setting with software commands. The Cisco 7000 series router accepts the VIP2. The Cisco 7500 series router accepts both the VIP2 and the VIP4. You can install either one or two PA-T3+ port adapters per VIP2 or VIP4. The PA-T3+ is a one-interface version.