CDP. Introduction to CDP. Layer 2 protocol that connects lower physical media and upper network layer protocols used to obtain information about neighboring devices, such as the types of devices connected router interfaces they are connected to interfaces used to make the connections
Each exclamation point (!) indicates a successful echo.
Each period (.) on the display indicates that the application on the router timed out while it waited for a packet echo from a target.
The traceroute command will attempt to reach the next step until the Ctrl-Shift-6 escape sequence is used.