Really kind of need that to connect to the console port. Do you know if it has an IP address configured? If you dont know the IP address and have access to another cisco router or switch hook the two together, then from the device you have access to do a show CDP neighbor dteail and if it has an ip configured it should tell you, then can telnet into it with a properly configured device. I dont recall but I think the default time for CDP updates is 90 seconds. That is if CDP is not disabled on the 2516.