Cisco Systems CCNA 2 4.1.2 Information obtained with CDP

4.1.2 Information obtained with CDP

CDP is used to collect information about directly-connected devices. The types of information

it collects are referred to as Type Length Values (TLVs). This TI includes a table that defines

each TLV. Certain types of information are only included as a part of CDPv2. This information

is noted in the table.

The show cdp neighbors command displays CDP information collected by a device about

its neighbors. It can be issued at a console connected to a Cisco network device.

Demonstrate the show cdp neighbors command and the show cdp neighbors

detail command. Note that much of the information outlined in the table can only be seen if

the detail option is utilized. This command variation is seen in subsequent RIOs. Some

information is only displayed with CDPv2, which is implemented with IOS version 12.0(3)T.

Demonstrate how the show cdp neighbors command and its variations can be consoled

into a router that is connected to another router or a switch to show students the output.

The show cdp neighbors command allows students to perform the associated Flash e-

Lab.

TLV Definition

Device-ID TLV Identifies the device name in the form of a

character string

Address TLV Contains a list of network address of both

receiving and transmitting devices

Port-ID TLV Identifies the port on which the CDP packet is

sent

Capabilities TLV Describes the functional capabilities of a device

in the form of a device type such as a switch

Version TLV Contains information about the software release

version on which the device is running

Platform TLV Describes the hardware platform name of the

device

IP Network Prefix TLV CDPv2 Contains a list of network prefixes to which the

sending device can forward IP packets. This

information is in the form of the interface

protocol and port number such as Eth 0/1

VTP Management Domain TLV

CDPv2 Advertises the configured VTP management

domain name string of a network and is used by

network operators to verify VTP domain

configuration in adjacent network nodes

Native VLAN TLV CDPv2 Indicates the assumed VLAN for untagged

packets on each interface and is implemented

only for interfaces the support the IEEE 802.1Q

protocol

Full or Half Duplex TLV Indicates the status duplex configuration of a

CDP broadcast interface and is used by network

administrators to diagnose connectivity

problems between adjacent network devices