Cisco Systems CCNA 2 manual Information obtained with CDP, Tlv

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.

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	Advertises the configured VTP management
CDPv2	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

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.

41 - 238 CCNA 2: Routers and Routing Basics v3.1 Instructor Guide – Module 4 Copyright ♥ 2004, Cisco Systems, Inc.