Catalyst 4500 Series Switch SW Configuration Guide, Release IOS-XE 3.2.xSG

Configuring CDP

This chapter describes how to configure Cisco Discovery Protocol (CDP) on the Catalyst 4500 series switch. It also provides guidelines, procedures, and configuration examples.

This chapter includes the following major sections:

•About CDP

•Configuring CDP

Note For complete syntax and usage information for the commands used in this chapter, refer to the
Cisco IOS Configuration Fundamentals Configuration Guide, Release 12.4:

http://www.cisco.com/en/US/docs/ios/fundamentals/configuration/guide/12_4/cf_12_4_book.html

and the Cisco IOS Configuration Fundamentals Command Reference, Release 12.2:

http://www.cisco.com/en/US/docs/ios/12_2/configfun/command/reference/ffun_r.html

Note For complete syntax and usage information for the switch commands used in this chapter, look at the Cisco Catalyst 4500 Series Switch Command Reference and related publications at this location:

http://www.cisco.com/en/US/products/hw/switches/ps4324/index.html

If the command is not found in the Catalyst 4500 Command Reference, it is located in the larger Cisco IOS library. Refer to the Catalyst 4500 Series Switch Cisco IOS Command Reference and related publications at this location:

http://www.cisco.com/en/US/products/ps6350/index.html

About CDP

CDP is a protocol that runs over Layer 2 (the data link layer) on all Cisco routers, bridges, access servers, and switches. CDP allows network management applications to discover Cisco devices that are neighbors of already known devices, in particular, neighbors running lower-layer, transparent protocols.With CDP, network management applications can learn the device type and the SNMP agent address of neighboring devices. CDP enables applications to send SNMP queries to neighboring devices.

CDP runs on all LAN and WAN media that support Subnetwork Access Protocol (SNAP).

Each CDP-configured device sends periodic messages to a multicast address. Each device advertises at least one address at which it can receive SNMP messages. The advertisements also contain the time-to-live, or holdtime information, which indicates the length of time a receiving device should hold CDP information before discarding it.

Configuring CDP

The following sections describe how to configure CDP:

•Enabling CDP Globally

•Displaying the CDP Global Configuration

•Enabling CDP on an Interface

•Displaying the CDP Interface Configuration

•Monitoring and Maintaining CDP

Enabling CDP Globally

To enable CDP globally, perform this task:

Switch(config)# [no] cdp run

This example shows how to enable CDP globally:

Switch(config)# cdp run

Displaying the CDP Global Configuration

To display the CDP configuration, perform this task:

Switch# show cdp

This example shows how to display the CDP configuration:

Switch# show cdp

Global CDP information:

        Sending CDP packets every 120 seconds

        Sending a holdtime value of 180 seconds

        Sending CDPv2 advertisements is enabled

Switch# 

For additional CDP show commands, see the "Monitoring and Maintaining CDP" section.

Enabling CDP on an Interface

To enable CDP on an interface, perform this task:

Switch(config-if)# [no] cdp enable

This example shows how to enable CDP on Fast Ethernet interface 5/1:

Switch(config)# interface fastethernet 5/1

Switch(config-if)# cdp enable 

This example shows how to disable CDP on Fast Ethernet interface 5/1:

Switch(config)# interface fastethernet 5/1

Switch(config-if)# no cdp enable 

Displaying the CDP Interface Configuration

To display the CDP configuration for an interface, perform this task:

Switch# show cdp interface [type/number]

This example shows how to display the CDP configuration of Fast Ethernet interface 5/1:

Switch# show cdp interface fastethernet 5/1

FastEthernet5/1 is up, line protocol is up

  Encapsulation ARPA

  Sending CDP packets every 120 seconds

  Holdtime is 180 seconds

Switch# 

Monitoring and Maintaining CDP

To monitor and maintain CDP on your device, perform one or more of these tasks:

Switch# clear cdp counters

Switch# clear cdp table

Switch# show cdp

Switch# show cdp entry entry_name 
[protocol | version]

Switch# show cdp interface 
[type/number] 

Switch# show cdp neighbors 
[type/number] [detail]

Switch# show cdp traffic

Switch# show debugging

This example shows how to clear the CDP counter configuration on your switch:

Switch# clear cdp counters

This example shows how to display information about the neighboring equipment:

Switch# show cdp neighbors

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

                  S - Switch, H - Host, I - IGMP, r - Repeater

Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID

JAB023807H1      Fas 5/3            127         T S       WS-C2948  2/46

JAB023807H1      Fas 5/2            127         T S       WS-C2948  2/45

JAB023807H1      Fas 5/1            127         T S       WS-C2948  2/44

JAB023807H1      Gig 1/2            122         T S       WS-C2948  2/50

JAB023807H1      Gig 1/1            122         T S       WS-C2948  2/49

JAB03130104      Fas 5/8            167         T S       WS-C4003  2/47

JAB03130104      Fas 5/9            152         T S       WS-C4003  2/48