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Cisco SCE 8000 10GBE Software Configuration Guide
OL-30621-02
Chapter 6 Global Configuration
Configuring Cisco Discovery Protocol
Configuring Cisco Discovery Protocol
Cisco Discovery Protocol (CDP)
is a device discovery protocol that runs on Cisco manufactured
equipment, and is now supported on the Cisco SCE 8000 platform.
•
Cisco Discovery Protocol, page 6-20
•
Cisco Discovery Protocol on the Cisco SCE 8000 Platform, page 6-21
•
Configuring CDP on the Cisco SCE 8000 Platform, page 6-22
•
Monitoring and Maintaining CDP, page 6-25
•
CDP Configuration Examples, page 6-27
Cisco Discovery Protocol
CDP is primarily used to obtain protocol addresses of neighboring devices and discover the platform of
those devices. It is media- and protocol-independent, and runs on all equipment manufactured by Cisco,
including routers, bridges, access servers, and switches.
CDP runs on all media that support Subnetwork Access Protocol (SNAP), including LAN, Frame Relay,
and ATM physical media. CDP runs over the data link layer only. Therefore, two systems that support
different network-layer protocols can learn about each other.
Each device configured for CDP sends periodic messages, known as advertisements, to a multicast
address. Each device advertises at least one address where it can receive SNMP messages. The
advertisements also contain time-to-live, or holdtime, information, which indicates the length of time a
receiving device should hold CDP information before discarding it. Each device also listens to the
periodic CDP messages sent by others in order to learn about neighboring devices and determine when
their interfaces to the media go up or down.
CDP Version-2 (CDPv2) is the most recent release of the protocol and provides more intelligent device
tracking features. These features include a reporting mechanism that allows for more rapid error
tracking, thereby reducing costly downtime. Reported error messages can be sent to the console or to a
logging server, and include instances of native VLAN IDs (IEEE 802.1Q) on connecting ports that do
not match, and port duplex states between connecting devices that do not match.
Type-Length-Value fields (TLVs) are blocks of information embedded in CDP advertisements.
summarizes the TLV definitions for CDP advertisements.
Table 6-1
Type-Length-Value Definitions for CDPv2
TLV
Definition
Device-ID TLV
Identifies the device name in the form of a character string.
Address TLV
Contains a list of network addresses of both receiving and
sending devices.
Port-ID TLV
Identifies the port on which the CDP packet is sent.
Capabilities TLV
Describes the functional capability for the device in the form of
a device type, for example, 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, for
example, Cisco 4500.