To troubleshoot the serial connection, send the <Ctrl + D> character to the serial port. The router should respond with something like 72 or 75 with some special characters at the beginning and at the end. The first character has ASCII code 0 × 15 (NAK) and the last one is 0 × 04 (EOT). If you see something like that, then you can assume that the serial port is configured properly. To troubleshoot the Ethernet connection, try pinging the router first and if you succeed then try connecting to the router via telnet. To end the telnet session, type logout.