Why Would A Network Administrator Issue The Show Cdp Neigbors Command On A Router?

Why would a network administrator issue the show CDP neighbors command on a router?​

• It can show the router ID and various information about the OSPF neighbors.
• It can show the information about the routing table and other directly connected Cisco devices.
• The line status and other directly connected Cisco devices information can be displayed with it.
• The directly connected cisco devices information and the device ID can display with it. 

Answer: The command show CDP gives the knowledge about the directly connected Cisco devices such as the device ID, local interface, capability, platforms, and the port ID of the remotely connected devices.

What is CDP?

CDP is known as a Cisco proprietary protocol that runs on the data link layer. Due to the CDP operation on the data link layer, more than two Cisco devices such as the router that supports various network-layer protocols, learn from each other whether or not Layer 3 connectivity is present.

When Cisco devices start-up, the CDP starts by default. CDP found the neighboring cisco devices automatically which runs the CDP rather than the type of the layer 3 protocol or suits are running or not. Another work of CDP is that it exchanges the hardware and the software information with the CDP neighbor who is directly linked.

The information provided by the CDP about its neighbor is in the following:

• Device identifier: the hostname of the switch which is configured.
• Address list: for up to one network layer address of supported protocol.
• Port identifier: it gives the information about the name of the local and remote port-in which is in form of ASCII character as the ethernet0.
• Capabilities list: it shows whether the device is the router or not.
• Platform: it shows the platform of the hardware i.e., a cisco 1841 series of the router.

The command shows cdp neighbor provide the information about the IP address of the neighboring devices. Despite the information, if you can ping the neighbor the CDP will show the IP address of the neighbor. The command is used when the router could not route across to their shared data link. The command show cdp neighbor will show if any of the CDP neighbors has the error in the IP configuration error.

To telnet in the device in the network discovery situation, the IP address of the CDP neighbor information is needed to know. But the CDP has been a security risk because some of the version of the IOS gives the CDP information by default that’s why it needed to know how to disable the CDP? For the disable of the CDP globally the global configuration command no cdp run is used. For the disable on interface level the command is no cdp enable.