| 4.1 |  | Discovering and Connecting to Neighbors |
| 4.1.2 |  | Information obtained with CDP |

| The primary use of CDP is to discover all Cisco devices that are directly connected to a local device. Use the show cdp neighbors command to display CDP updates on the local device. Figure displays an example of how CDP delivers its collection of information to a network administrator. Each router that is running CDP exchanges protocol information with its neighbors. The network administrator can display the results of this CDP information exchange on a console that is connected to a local router. The administrator uses the show cdp neighbors command to display information about the networks directly connected to the router. CDP provides information about each CDP neighbor device by transmitting type length values (TLVs), which are blocks of information embedded in CDP advertisements. Device TLVs displayed by the show cdp neighbors command include the following: Device ID Local Interface Holdtime Capability Platform Port ID VTP Management Domain Name (CDPv2 only) Native VLAN (CDPv2 only) Full/Half-Duplex (CDPv2 only) Notice that the lowest router in the figure is not directly connected to the administrator’s console router. To obtain CDP information about this device, the administrator would need to Telnet to a router that is directly connected to this device.
| Web Links CDP Commands http://www.cisco.com/en/US/ products/sw/ iosswrel/ps1831/ products_command_ reference_ chapter09186a00800d983f.html