Cisco Nexus 1000V System Management Configuration Guide, Release 4.2(1)SV1(5.1)
Configuring the CDP
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Table Of Contents

Configuring CDP

Information About CDP

High Availability

Guidelines and Limitations

Defaults

Configuring CDP

CDP Global Configuration

Enabling or Disabling CDP Globally

Advertising a CDP Version

Configuring CDP Options

CDP Interface Configuration

Enabling CDP on an Interface

Disabling CDP on an Interface

Monitoring CDP

Clearing CDP Statistics

Verifying the CDP Configuration

Configuration Example for CDP

Additional References

Related Documents

Standards

Feature History for CDP


Configuring CDP


This chapter describes how to configure the Cisco Discovery Protocol (CDP), and includes the following sections:

Information About CDP

Guidelines and Limitations

Defaults

Configuring CDP

Monitoring CDP

Verifying the CDP Configuration

Configuration Example for CDP

Additional References

Information About CDP

Cisco Discovery Protocol (CDP) runs over the data link layer and is used to advertise information to all attached Cisco devices, and to discover and view information about attached Cisco devices. CDP runs on all Cisco-manufactured equipment.

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 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 discarding 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

All CDP packets include a VLAN ID. The CDP packet is untagged, so it goes over the native/access VLAN, which is then also added to the packet.

For more information on VLANs, see the Cisco Nexus 1000V Layer 2 Switching Configuration Guide, Release 4.2(1)SV1(5.1).

High Availability

Stateless restarts are supported for CDP. After a reboot or a supervisor switchover, the running configuration is applied.

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 globally before you can configure CDP on an interface. CDP is enabled globally by default, but can be disabled using the "Enabling or Disabling CDP Globally" procedure.

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

Defaults

Table 2-1 lists the CDP default settings.

Table 2-1 CDP Defaults  

Parameters
Default

CDP

Enabled globally and on all interfaces

CDP version

Version 2

CDP device ID

System name

CDP timer

60 seconds

CDP hold timer

180 seconds


Configuring CDP

This section includes the following topics:

CDP Global Configuration

Enabling CDP on an Interface

Disabling CDP on an Interface

CDP Global Configuration

This section includes the following topics:

Enabling or Disabling CDP Globally

Advertising a CDP Version

Configuring CDP Options

Enabling or Disabling CDP Globally

Use this procedure to enable or disable CDP globally.Although CDP is enabled globally by default, should it be disabled, you can use this procedure to enable it again.

BEFORE YOU BEGIN

Before beginning this procedure, you must know or do the following:

You are logged in to the CLI in EXEC mode.

CDP must be enabled globally before you can configure it on an interface.

When you globally disable the CDP feature, all CDP configurations are removed.

SUMMARY STEPS

1. config t

2. [no] cdp enable

DETAILED STEPS

 
Command
Purpose

Step 1 

config t

Example:

n1000v# config t

n1000v(config)#

Places you in the CLI Global Configuration mode.

Step 2 

[no] cdp enable

Example:

n1000v(config)# cdp enable

Example:

n1000v(config)# no cdp enable

Enables or disables the CDP feature globally.

Advertising a CDP Version

Use this procedure to designate the CDP version to advertise on the device.

BEFORE YOU BEGIN

Before beginning this procedure, you must know or do the following:

You know the version of CDP currently supported on the device.

Only one version of CDP (version 1 or version 2) is advertised at a time for all uplinks and port channels on the switch.

For more information about CDP, see the "Information About CDP" section.

SUMMARY STEPS

1. config t

2. cdp advertise {v1 | v2}

3. (Optional) show cdp global

4. (Optional) copy running-config startup-config

DETAILED STEPS

 
Command
Purpose

Step 1 

config t

Example:

n1000v# config t

n1000v(config)#

Places you in the CLI Global Configuration mode.

Step 2 

cdp advertise {v1 | v2}

Example 1:

n1000v(config)# cdp advertise v1

n1000v(config)#

Example 2:

n1000v(config)# cdp advertise v2

n1000v(config)#

Assigns the CPD version to advertise.

CDP Version 1

CDP Version 2

Step 3 

show cdp global

(Optional) Displays the CDP configuration, indicating the CDP version that is being advertised or sent to other devices.

 

Example 1:

n1000v(config)# show cdp global

Global CDP information:

CDP enabled globally

Sending CDP packets every 60 seconds

Sending a holdtime value of 180 seconds

Sending CDPv2 advertisements is disabled

Sending DeviceID TLV in Default Format

Example 2:

n1000v(config)# show cdp global

Global CDP information:

CDP enabled globally

Sending CDP packets every 60 seconds

Sending a holdtime value of 180 seconds

Sending CDPv2 advertisements is enabled

Sending DeviceID TLV in Default Format

Step 4 

copy running-config startup-config

Example:

n1000v(config)# copy running-config startup-config

(Optional) Saves the running configuration persistently through reboots and restarts by copying it to the startup configuration.

Configuring CDP Options

Use this procedure to configure the following for CDP:

the device ID format to use


Note Only the system-name device ID format is supported.


the maximum hold time for neighbor information

the refresh time for sending advertisements

BEFORE YOU BEGIN

Before beginning this procedure, you must know or do the following:

You can view output from upstream cat6k switch using the show cdp neighbor command.

If you are setting the holdtime, you know how long you want CDP to retain neighbor information.

If you are setting the CDP timer, you know how often you want CDP to advertise.

For more information about CDP, see the "Information About CDP" section.

SUMMARY STEPS

1. config t

2. (Optional) cdp format device-id system-name

3. show cdp neighbors from the upstream device

4. show cdp neighbors from your device

5. (Optional) cdp timer seconds

6. (Optional) cdp holdtime seconds

7. (Optional) show cdp global

8. (Optional) copy running-config startup-config

DETAILED STEPS

 
Command
Purpose

Step 1 

config t

Example:

n1000v# config t

n1000v(config)#

Places you in the CLI Global Configuration mode.

Step 2 

cdp format device-id system-name

Example:

n1000v(config)# cdp format device-id system-name

n1000v(config)#

(Optional) Specifies that CDP uses the system name for the device ID format.

Step 3 

show cdp neighbors

Displays your device from the upstream device.

 

Example:

swordfish-6k-2#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
 
      
Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
 
      
02000c000000     Gig 1/16          14             S       Soft Swit Eth 2/4
02000c000000     Gig 1/17          14             S       Soft Swit Eth 2/5
02000c000000     Gig 1/14          14             S       Soft Swit Eth 2/2
02000c000000     Gig 1/15          14             S       Soft Swit Eth 2/3
02000c000000     Gig 1/18          13             S       Soft Swit 

Step 4 

show cdp neighbors

Displays the upstream device from your device,

 
n1000v(config)# 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
 
      
swordfish-6k-2         Eth2/2          169     R S I    WS-C6503-E    Gig1/14 
swordfish-6k-2         Eth2/3          139     R S I    WS-C6503-E    Gig1/15 
swordfish-6k-2         Eth2/4          135     R S I    WS-C6503-E    Gig1/16 
swordfish-6k-2         Eth2/5          177     R S I    WS-C6503-E    Gig1/17 
swordfish-6k-2         Eth2/6          141     R S I    WS-C6503-E    Gig1/18 

Step 5 

cdp holdtime seconds

Example:

n1000v(config)# cdp holdtime 10

(Optional) Sets the maximum amount of time that CDP holds onto neighbor information before discarding it.

The range is from 10 to 255 seconds.

The default is 180 seconds.

Step 6 

cdp timer seconds

Example:

n1000v(config)# cdp timer 5

(Optional) Sets the refresh time for CDP to send advertisements to neighbors.

The range is from 5 to 254 seconds.

The default is 60 seconds.

Step 7 

show cdp global

Displays the global CDP configuration.

 

Example:

n1000v(config)# show cdp global

Global CDP information:

CDP enabled globally

Sending CDP packets every 5 seconds

Sending a holdtime value of 10 seconds

Sending CDPv2 advertisements is disabled

Sending DeviceID TLV in Mac Address Format

Step 8 

copy running-config startup-config

Example:

n1000v(config-if)# copy running-config startup-config

(Optional) Saves the running configuration persistently through reboots and restarts by copying it to the startup configuration.

CDP Interface Configuration

This section includes the following procedures:

Enabling CDP on an Interface

Disabling CDP on an Interface

Enabling CDP on an Interface

Use this procedure to enable CDP on a specific interface. Although CDP is enabled by default on all interfaces, should it become disabled, you can use this procedure to enable it again.

BEFORE YOU BEGIN

Before beginning this procedure, you must know or do the following:

The CDP feature is enabled globally. CDP is enabled globally by default, but can also be re-enabled using the "Enabling or Disabling CDP Globally" procedure.

For more information about CDP, see the "Information About CDP" section.

SUMMARY STEPS

1. config t

2. interface interface-type number

3. no cdp enable

4. cdp enable

5. show cdp interface interface-type number

6. copy running-config startup-config

DETAILED STEPS

 
Command
Purpose

Step 1 

config t

Example:

n1000v# config t

n1000v(config)#

Places you in the CLI Global Configuration mode.

Step 2 

interface interface-type number

Example:

n1000v(config)# interface port-channel 2

n1000v(config-if)#

Places you in the CLI Interface Configuration mode for the specific interface.

Step 3 

no cdp enable

Example:

n1000v(config-if)# no cdp enable

Disables CDP on this interface.

Step 4 

cdp enable

Example:

n1000v(config-if)# cdp enable

Enables CDP on this interface.

Step 5 

show cdp interface interface-type number

Example:

n1000v(config-if)# show cdp interface mgmt0

mgmt0 is up

CDP disabled on interface

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

(Optional) Displays CDP information for the specified interface.

Step 6 

copy running-config startup-config

Example:

n1000v(config-if)# copy running-config startup-config

(Optional) Saves the running configuration persistently through reboots and restarts by copying it to the startup configuration.

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

n1000v# config t

n1000v(config)# interface port-channel 2

n1000v(config-if)# no cdp enable

n1000v(config-if)# cdp enable

n1000v(config-if)# copy running-config startup-config

 
 

Disabling CDP on an Interface

Use this procedure to disable CDP on a specific interface.

BEFORE YOU BEGIN

Before beginning this procedure, you must know or do the following:

CDP is currently enabled on the device.


Note If CDP is disabled on the device, then it is also disabled for all interfaces.


CDP is currently enabled on the specific interface you want to configure.

For more information about CDP, see the "Information About CDP" section.

SUMMARY STEPS

1. config t

2. interface interface-type number

3. no cdp enable

4. (Optional) show cdp interface interface-type number

5. (Optional) copy running-config startup-config

DETAILED STEPS

 
Command
Purpose

Step 1 

config t

Example:

n1000v# config t

n1000v(config)#

Places you in the CLI Global Configuration mode.

Step 2 

interface interface-type number

Example:

n1000v(config)# interface mgmt0

n1000v(config-if)#

Places you in the CLI Interface Configuration mode for the specified interface.

Step 3 

no cdp enable

Example:

n1000v(config-if)# no cdp enable

Disables CDP on the specified interface.

Step 4 

show cdp interface interface-type number

Example:

n1000v(config-if)# show cdp interface mgmt0

(Optional) Displays CDP information for an interface.

Step 5 

copy running-config startup-config

Example:

n1000v(config-if)# copy running-config startup-config

(Optional) Saves the running configuration persistently through reboots and restarts by copying it to the startup configuration.

This example shows how to disable CDP on mgmt0:

n1000v# config t

n1000v(config)# interface mgmt0

n1000v(config-if)# no cdp enable

n1000v(config-if)# show cdp interface mgmt0

mgmt0 is up

CDP disabled on interface

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

n1000v(config-if)# copy running-config startup-config

 
 

Monitoring CDP

To monitor CDP traffic, use the following command:

Command
Purpose

show cdp traffic interface interface-type slot/port

Displays the CDP traffic statistics on an interface.

See Example 2-7


Clearing CDP Statistics

To clear CDP statistics, use one of the following commands.

Command
Purpose

clear cdp counters

Clears CDP statistics on all interfaces.

clear cdp counters interface number

Clears CDP statistics on the specified interface.

clear cdp table

Clears the CDP cache for one or all interfaces.


Verifying the CDP Configuration

To verify the CDP configuration, use one of the following commands:

Command
Purpose

show cdp all

Displays all interfaces that have CDP enabled.

See Example 2-1

show cdp entry {all | name entry-name}

Displays the CDP database entries.

See Example 2-2

show cdp global

Displays the CDP global parameters.

See Example 2-4

show cdp interface interface-type slot/port

Displays the CDP interface status.

See Example 2-5

show cdp neighbors {detail | interface interface-type slot/port}

Displays the CDP neighbor status.

See Example 2-6


Example 2-1 show cdp all

n1000v# show cdp all
Ethernet2/2 is up
    CDP enabled on interface
    Sending CDP packets every 60 seconds
    Holdtime is 180 seconds
Ethernet2/3 is up
    CDP enabled on interface
    Sending CDP packets every 60 seconds
    Holdtime is 180 seconds
Ethernet2/4 is up
    CDP enabled on interface
    Sending CDP packets every 60 seconds
    Holdtime is 180 seconds
Ethernet2/5 is up
    CDP enabled on interface
    Sending CDP packets every 60 seconds
    Holdtime is 180 seconds
Ethernet2/6 is up
    CDP enabled on interface
    Sending CDP packets every 60 seconds
    Holdtime is 180 seconds
mgmt0 is up
    CDP enabled on interface
    Sending CDP packets every 60 seconds
    Holdtime is 180 seconds
 
 

Example 2-2 show cdp entry name

n1000v# show cdp entry name swordfish-6k-2
----------------------------------------
Device ID:swordfish-6k-2
System Name:
Interface address(es):
    IPv4 Address: 172.28.30.2
Platform: cisco WS-C6503-E, Capabilities: Router Switch IGMP Filtering 
Interface: Ethernet2/2, Port ID (outgoing port): GigabitEthernet1/14
Holdtime: 152 sec
 
 
Version:
Cisco IOS Software, s72033_rp Software (s72033_rp-IPBASE-M), Version 12.2(33)SXH2a, 
RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Fri 25-Apr-08 09:11 by prod_rel_team
 
 

Example 2-3 show cdp entry all

n1000v# show cdp entry all
----------------------------------------
Device ID:swordfish-6k-2
System Name:
Interface address(es):
    IPv4 Address: 172.28.30.2
Platform: cisco WS-C6503-E, Capabilities: Router Switch IGMP Filtering 
Interface: Ethernet2/2, Port ID (outgoing port): GigabitEthernet1/14
Holdtime: 140 sec
 
 
Version:
Cisco IOS Software, s72033_rp Software (s72033_rp-IPBASE-M), Version 12.2(33)SXH2a, 
RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Fri 25-Apr-08 09:11 by prod_rel_team
 
 
Advertisement Version: 1
 
 
----------------------------------------
Device ID:swordfish-6k-2
System Name:
Interface address(es):
    IPv4 Address: 172.28.30.2
Platform: cisco WS-C6503-E, Capabilities: Router Switch IGMP Filtering 
Interface: Ethernet2/3, Port ID (outgoing port): GigabitEthernet1/15
Holdtime: 129 sec
 
 
Version:
Cisco IOS Software, s72033_rp Software (s72033_rp-IPBASE-M), Version 12.2(33)SXH2a, 
RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Fri 25-Apr-08 09:11 by prod_rel_team
 
 
Advertisement Version: 1
 
 
----------------------------------------
Device ID:swordfish-6k-2
System Name:
Interface address(es):
    IPv4 Address: 7.7.8.1
Platform: cisco WS-C6503-E, Capabilities: Router Switch IGMP Filtering 
Interface: Ethernet2/4, Port ID (outgoing port): GigabitEthernet1/16
Holdtime: 154 sec
 
 
Version:
Cisco IOS Software, s72033_rp Software (s72033_rp-IPBASE-M), Version 12.2(33)SXH2a, 
RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Fri 25-Apr-08 09:11 by prod_rel_team
 
 
Advertisement Version: 1
 
 
----------------------------------------
Device ID:swordfish-6k-2
System Name:
Interface address(es):
    IPv4 Address: 7.7.8.1
Platform: cisco WS-C6503-E, Capabilities: Router Switch IGMP Filtering 
Interface: Ethernet2/5, Port ID (outgoing port): GigabitEthernet1/17
Holdtime: 156 sec
 
 
Version:
Cisco IOS Software, s72033_rp Software (s72033_rp-IPBASE-M), Version 12.2(33)SXH2a, 
RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Fri 25-Apr-08 09:11 by prod_rel_team
 
 
Advertisement Version: 1
 
 
----------------------------------------
Device ID:swordfish-6k-2
System Name:
Interface address(es):
    IPv4 Address: 172.28.15.229
Platform: cisco WS-C6503-E, Capabilities: Router Switch IGMP Filtering 
Interface: Ethernet2/6, Port ID (outgoing port): GigabitEthernet1/18
Holdtime: 171 sec
 
 
Version:
Cisco IOS Software, s72033_rp Software (s72033_rp-IPBASE-M), Version 12.2(33)SXH2a, 
RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Fri 25-Apr-08 09:11 by prod_rel_team
 
 
Advertisement Version: 1
 
 

Example 2-4 show cdp global

n1000v(config)# show cdp global 
Global CDP information:
    CDP enabled globally
    Sending CDP packets every 60 seconds
    Sending a holdtime value of 180 seconds
    Sending CDPv2 advertisements is disabled
    Sending DeviceID TLV in Default Format
 
 

Example 2-5 show cdp interface

n1000v(config)# show cdp interface ethernet 2/3
Ethernet2/3 is up
    CDP enabled on interface
    Sending CDP packets every 60 seconds
    Holdtime is 180 seconds
 
 

Example 2-6 show cdp neighbors interface

n1000v(config)# show cdp neighbors interface ethernet 2/3
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
 
 
swordfish-6k-2         Eth2/3          173     R S I    WS-C6503-E    Gig1/15 
 
 
 
 

Example 2-7 show cdp traffic interface

n1000v(config)# show cdp traffic interface ethernet 2/3
----------------------------------------
Traffic statistics for Ethernet2/3
Input Statistics:
    Total Packets: 98
    Valid CDP Packets: 49
        CDP v1 Packets: 49
        CDP v2 Packets: 0
    Invalid CDP Packets: 49
        Unsupported Version: 49
        Checksum Errors: 0
        Malformed Packets: 0
 
 
Output Statistics:
    Total Packets: 47
        CDP v1 Packets: 47
        CDP v2 Packets: 0
    Send Errors: 0

Configuration Example for CDP

This example enables the CDP feature and configures the refresh and hold timers:

config t

cdp enable

cdp timer 50

cdp holdtime 100

Additional References

This section includes the following additional information related to CDP:

Related Documents

Standards

Related Documents

Related Topic
Document Title

VLAN

Cisco Nexus 1000V Layer 2 Switching Configuration Guide, Release 4.2(1)SV1(5.1)

Complete command syntax, command modes, command history, defaults, usage guidelines, and examples

Cisco Nexus 1000V Command Reference, Release 4.2(1)SV1(5.1)


Standards

Standards
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.


Feature History for CDP

This section provides the CDP feature release history.

Feature Name
Releases
Feature Information

CDP

4.0(4)SV1(1)

This feature was introduced.