Configuring Cisco Discovery Protocol

Revised June 30, 2011

Cisco Discovery Protocol (CDP) is primarily used to obtain protocol addresses of neighboring devices and to discover the platform of those devices. CDP is media- and protocol-independent, and it runs on all Cisco-manufactured equipment including routers, bridges, access servers, and switches. By using CDP, a device can advertise its existence to other devices and receive information about other devices on the same LAN or on the remote side of a WAN.

Use of SNMP with the CDP Management Information Base (MIB) allows network management applications to learn the device type and the SNMP agent address of neighboring devices, and to send SNMP queries to those devices. Cisco Discovery Protocol uses the CISCO-CDP-MIB.

Each device that is configured for CDP sends periodic "hello" messages, known as advertisements, to a multicast address. Each device advertises at least one address at which it can receive SNMP messages. The advertisements also contain time-to-live, or hold-time, information to indicate the length of time a receiving device should hold the CDP information before discarding it. Each device also listens to the periodic CDP messages that are sent by others in order to learn about neighboring devices, and to determine when their interfaces to the media go up or down.

This chapter includes the following sections:

•Configuring CDP

•Displaying the CDP Configuration

Configuring CDP

By default, CDP is enabled on the Bond 0 interface of each Cisco TelePresence Exchange System server.

Before You Begin

•CDP configurations are not replicated between servers. When you change the CDP configuration, you must manually apply the same configuration changes to each of the other servers.

•To see the current CDP configuration, see the "Displaying the CDP Configuration" section.

Procedure

Step 1 Log in to the CLI of the server.

Step 2 To see which interfaces are available for you to enable CDP, enter show cdp list. 

admin: show cdp list 

  Available Interfaces:

     bond0

     bond1

Step 3 To enable or disable CDP on one or all interfaces, enter the following command:

set cdp {enable | disable} {interface | all}

To specify an interface, enter one of the values in the CLI output from when you completed Step 2.

Step 4 To set the frequency of CDP advertisements, enter the following command:

set cdp timer seconds

Step 5 To set the advertised amount of time that a receiving device should hold the information that is sent by this device before discarding it, enter the following command:

set cdp holdtime seconds

Step 6 To verify the configuration, proceed to the "Displaying the CDP Configuration" section.

Related Topics

•Command Reference, page C-1

Displaying the CDP Configuration

Procedure

Step 1 Log in to the CLI of the server.

Step 2 To see the current CDP configuration, enter show cdp config. 

admin: show cdp config 

  CDP Configuration: Enabled

 

    Hello Timer : 60 seconds

    Hold Time   : 180 seconds

    Enabled on  : bond0

Related Topics

•Command Reference, page C-1