Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 6.x
Configuring CDP
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Table Of Contents

Configuring CDP

Information About CDP

CDP Overview

VTP Feature Support

High Availability

Virtualization Support

Licensing Requirements for CDP

Prerequisites for CDP

Guidelines and Limitations

Default Settings

Configuring CDP

Enabling or Disabling CDP Globally

Enabling or Disabling CDP on an Interface

Configuring Optional CDP Parameters

Verifying the CDP Configuration

Configuration Example for CDP

Additional References

Related Documents

MIBs

Feature History for CDP


Configuring CDP


This chapter describes how to configure the Cisco Discovery Protocol (CDP) on Cisco NX-OS devices.

This chapter includes the following sections:

Information About CDP

Licensing Requirements for CDP

Prerequisites for CDP

Guidelines and Limitations

Default Settings

Configuring CDP

Verifying the CDP Configuration

Configuration Example for CDP

Additional References

Feature History for CDP

Information About CDP

This section includes the following topics:

CDP Overview

VTP Feature Support

High Availability

Virtualization Support

CDP Overview

The Cisco Discovery Protocol (CDP) is a media-independent and protocol-independent protocol that runs on all Cisco-manufactured equipment including routers, bridges, access and communication servers, and switches. You can use CDP to discover and view information about all the Cisco devices that are directly attached to the device.

CDP gathers protocol addresses of neighboring devices and discovers the platform of those devices. CDP runs over the data link layer only. Two systems that support different Layer 3 protocols can learn about each other.

Each device that you configure for CDP sends periodic advertisements to a multicast address. Each device advertises at least one address at which it can receive SNMP messages. The advertisements also contain hold-time information, which indicates the length of time that a receiving device should hold CDP information before removing it. You can configure the advertisement or refresh timer and the hold timer.

CDP Version-2 (CDPv2) allows you to track instances where the native VLAN ID or port duplex states do not match between connecting devices.

CDP advertises the following type-length-value fields (TLVs):

Device ID

Address

Port ID

Capabilities

Version

Platform

Native VLAN

Full/Half Duplex

MTU

SysName

SysObjectID

Management Address

Physical Location

VTP

All CDP packets include a VLAN ID. If you configure CDP on a Layer 2 access port, the CDP packets sent from that access port include the access port VLAN ID. If you configure CDP on a Layer 2 trunk port, the CDP packets sent from that trunk port include the lowest configured VLAN ID allowed on that trunk port. The trunk port can receive CDP packets that include any VLAN ID in the allowed VLAN list for that trunk port. For more information on VLANs, see the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide.

VTP Feature Support

CDP sends the VLAN Trunking Protocol (VTP) type-length-value field (TLV) if the following conditions are met:

CDP Version 2 is enabled

The VTP feature is enabled

A VTP domain name is configured

You can view the VTP information with the show cdp neighbors detail command.

High Availability

Cisco NX-OS supports stateless restarts for CDP. After a reboot or a supervisor switchover, Cisco NX-OS applies the running configuration. For more information on high availability, see the Cisco Nexus 7000 Series NX-OS High Availability and Redundancy Guide.

Virtualization Support

Cisco NX-OS supports multiple instances of CDP, one instance per virtual device context (VDC). By default, Cisco NX-OS places you in the default VDC unless you specifically configure another VDC. For more information on VDCs, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide.

Licensing Requirements for CDP

Product
License Requirement

Cisco NX-OS

CDP requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.


Prerequisites for CDP

CDP has the following prerequisites:

If you configure VDCs, install the appropriate license and enter the desired VDC. See the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide for configuration information and the Cisco NX-OS Licensing Guide for licensing information.

Guidelines and Limitations

CDP has the following configuration guidelines and limitations:

CDP can discover up to 256 neighbors per port if the port is connected to a hub with 256 connections.

CDP must be enabled on the device or you cannot enable it on any interfaces.

You can configure CDP on physical interfaces and port channels only.

CDP is not supported for the Cisco Nexus 2000 Series Fabric Extender.

Default Settings

Table 5-1 lists the CDP default settings.

Table 5-1 CDP Default Settings

Parameters
Default

CDP

Enabled globally and on all interfaces

CDP version

Version 2

CDP device ID

Serial number

CDP timer

60 seconds

CDP hold timer

180 seconds


Configuring CDP

This section includes the following topics:

Enabling or Disabling CDP Globally

Enabling or Disabling CDP on an Interface

Configuring Optional CDP Parameters


Note Be aware that the Cisco NX-OS commands may differ from the Cisco IOS commands.


Enabling or Disabling CDP Globally

CDP is enabled by default. You can disable CDP and then reenable it.

You must enable CDP on the device before you enable CDP on any interfaces. If CDP is disabled globally and you enable CDP on specified interfaces, CDP will not be active on those interfaces; the system does not return an error message.

BEFORE YOU BEGIN

Make sure that you are in the correct VDC. To change the VDC, use the switchto vdc command.

SUMMARY STEPS

1. config t

2. cdp enable

3. copy running-config startup-config

DETAILED STEPS

 
Command
Purpose

Step 1 

config t

Example:

switch# config t

Enter configuration commands, one per line. End with CNTL/Z.

switch(config)#

Places you in global configuration mode.

Step 2 

cdp enable

Example:

switch(config)# cdp enable

Enables the CDP feature on the entire device. This is enabled by default.

Step 3 

copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

(Optional) Saves this configuration change.

Use the no cdp enable command to disable the CDP feature on the device.

Command
Purpose

no cdp enable

Example:

switch(config)# no cdp enable

Disables the CDP feature on the device.


This example shows how to enable the CDP feature:

switch# config t

Enter configuration commands, one per line. End with CNTL/Z.

switch(config)# cdp enable

 
 

Enabling or Disabling CDP on an Interface

CDP is enabled by default on an interface. You can disable CDP on an interface.

If CDP is disabled globally and you enable CDP on specified interfaces, CDP will not be active on those interfaces; the system does not return an error message.

BEFORE YOU BEGIN

Make sure that you are in the correct VDC. To change the VDC, use the switchto vdc command.

SUMMARY STEPS

1. config t

2. interface interface-type slot/port

3. cdp enable

4. show cdp interface interface-type slot/port

5. copy running-config startup-config

DETAILED STEPS

 
Command
Purpose

Step 1 

config t

Example:

switch# config t

Enter configuration commands, one per line. End with CNTL/Z.

switch(config)#

Places you in global configuration mode.

Step 2 

interface interface-type slot/port

Example:

switch(config)# interface ethernet 1/2

switch(config-if)#

Enters interface configuration mode.

Step 3 

cdp enable

Example:

switch(config-if)# cdp enable

Enables CDP on this interface. This is enabled by default.

Note Ensure that CDP is enabled on the device (see the "Enabling or Disabling CDP Globally" section).

Step 4 

show cdp interface interface-type slot/port

Example:

switch(config-if)# show cdp interface ethernet 1/2

(Optional) Displays CDP information for an interface.

Step 5 

copy running-config startup-config

Example:

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

This example shows how to disable CDP on Ethernet 1/2:

switch# config t

Enter configuration commands, one per line. End with CNTL/Z.

switch(config)# interface ethernet 1/2

switch(config-if)# no cdp enable

switch(config-if)# copy running-config startup-config

 
 

This example shows how to enable CDP on port channel 2:

switch# config t

Enter configuration commands, one per line. End with CNTL/Z.

switch(config)# interface port-channel 2

switch(config-if)# cdp enable

switch(config-if)# copy running-config startup-config

 
 

Configuring Optional CDP Parameters

You can use the following optional commands in global configuration mode to modify CDP:

Command
Purpose

cdp advertise {v1 | v2}

Example:

switch(config)# cdp advertise v1

Sets the CDP version supported by the device. The default is v2.

cdp format device-id {mac-address | serial-number | system-name}

Example:

switch(config)# cdp format device-id mac-address

Sets the CDP device ID. The options are as follows:

mac-address—MAC address of the chassis.

serial-number—Chassis serial number/Organizationally Unique Identifier (OUI).

system-name—The system name or fully qualified domain name.

The default displays system-name and serial-number information.

cdp holdtime seconds

Example:

switch(config)# cdp holdtime 150

Sets the time that CDP holds onto neighbor information before removing it. The range is from 10 to 255 seconds. The default is 180 seconds.

cdp timer seconds

Example:

switch(config)# cdp timer 50

Sets the refresh time when CDP sends advertisements to neighbors. The range is from 5 to 254 seconds. The default is 60 seconds.


Verifying the CDP Configuration

To display the CDP configuration, perform one of the following tasks:

Command
Purpose

show cdp all

Displays all interfaces that have CDP enabled.

show cdp entry {all | name entry-name}

Displays the CDP database entries.

show cdp global

Displays the CDP global parameters.

show cdp interface interface-type slot/port

Displays the CDP interface status.

show cdp neighbors {device-id | interface interface-type slot/port} [detail]

Displays the CDP neighbor status.

show cdp traffic interface interface-type slot/port

Displays the CDP traffic statistics on an interface.


Use the clear cdp counters command to clear CDP statistics on an interface.

Use the clear cdp table command to clear the CDP cache for one or all interfaces.

Configuration Example for CDP

This example shows how to enable the CDP feature and configure the refresh and hold timers:

config t
cdp enable
cdp timer 50
cdp holdtime 100
 
 

This example shows how to display the CDP global parameters:

switch# show cdp neighbors
 
 
Capability Codes: R - Router, T - Trans-Bridge, B - Source-Route-Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater,
                  V - VoIP-Phone, D - Remotely-Managed-Device,
                  s - Supports-STP-Dispute
 
 
Device-ID          Local Intrfce  Hldtme Capability  Platform      Port ID
Mgmt-switch
                   mgmt0          148    R S I     WS-C4948-10GE Gig1/37
    
switch88(FOX1518GRE6)
                   Eth1/25        164    R S I s   N5K-C5596UP   Eth1/25
    
switch89(FOX1518GQJ2)
                   Eth1/26        163    R S I s   N5K-C5596UP   Eth1/25
 
 

Additional References

For additional information related to implementing CDP, see the following sections:

Related Documents

MIBs

Related Documents

Related Topic
Document Title

CDP CLI commands

Cisco Nexus 7000 Series NX-OS System Management Command Reference

VDCs and VRFs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide


MIBs

MIBs
MIBs Link

CISCO-CDP-MIB

To locate and download MIBs, go to the following URL:

http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml


Feature History for CDP

Table 5-2 lists the release history for this feature.

Table 5-2 Feature History for CDP

Feature Name
Releases
Feature Information

CDP support for VTP domain name

4.2(1)

CDP advertises the VLAN Trunking Protocol (VTP) type-length-value field (TLV) in CDP version-2 packets.

See VTP Feature Support.