Feedback
Table Of Contents
CDP Commands
This chapter describes commands used to monitor the router and network using Cisco Discovery Protocol (CDP).
For system management configuration tasks and examples, refer to the "Configuring Cisco Discovery Protocol" chapter in the Release 12.2 Cisco IOS Configuration Fundamentals Configuration Guide.
cdp advertise-v2
To enable Cisco Discovery Protocol Version 2 (CDPv2) advertising functionality on a device, use the cdp advertise-v2 global configuration command. To disable advertising CDPv2 functionality, use the no form of the command.
cdp advertise-v2
no cdp advertise-v2
Syntax Description
This command has no arguments or keywords.
Defaults
Enabled
Command Modes
Global configuration
Command History
Usage Guidelines
CDP Version 2 has three additional type-length values (TLVs): they are VTP Management Domain Name, Native VLAN, and full/half-Duplex.
Examples
In the following example, CDP Version 2 advertisements are diabled on the router:
Router#show cdpGlobal CDP information:Sending CDP packets every 60 secondsSending a holdtime value of 180 secondsSending CDPv2 advertisements is enabledRouter#configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)#no cdp advertise-v2Router(config)#endRouter#show cdpGlobal CDP information:Sending CDP packets every 60 secondsSending a holdtime value of 180 secondsSending CDPv2 advertisements is not enabledRouter#Related Commands
cdp enable
To enable Cisco Discovery Protocol (CDP) on an interface, use the cdp enable interface configuration command. To disable CDP on an interface, use the no form of this command.
cdp enable
no cdp enable
Syntax Description
This command has no arguments or keywords.
Defaults
Enabled at the global level and on all supported interfaces.
Command Modes
Interface configuration
Command History
Usage Guidelines
CDP is enabled by default at the global level and on each supported interface in order to send or receive CDP information. However, some interfaces, such as ATM interfaces, do not support CDP.
Note
The cdp enable, cdp timer, and cdp run commands affect the operation of the IP on demand routing feature (that is, the router odr global configuration command). For more information on the router odr command, see the "On-Demand Routing Commands" chapter in the Cisco IOS IP and IP Routing Command Reference.
Examples
In the following example, CDP is disabled on the Ethernet 0 interface only:
Router#show cdpGlobal CDP information:Sending CDP packets every 60 secondsSending a holdtime value of 180 secondsSending CDPv2 advertisements is enabledRouter#config terminalRouter(config)#interface ethernet 0Router(config-if)#no cdp enableRelated Commands
Reenables CDP on a Cisco device.
Specifies how often the Cisco IOS software sends CDP updates.
router odr
Enables on-demand routing on a hub router.
cdp holdtime
To specify the amount of time the receiving device should hold a Cisco Discovery Protocol (CDP) packet from your router before discarding it, use the cdp holdtime global configuration command. To revert to the default setting, use the no form of this command.
cdp holdtime seconds
no cdp holdtime
Syntax Description
Defaults
180 seconds
Command Modes
Global configuration
Command History
Usage Guidelines
CDP packets are sent with a time to live, or hold time, value. The receiving device will discard the CDP information in the CDP packet after the hold time has elapsed.
You can set the hold time lower than the default setting of 180 seconds if you want the receiving devices to update their CDP info more rapidly.
The CDP hold time must be set to a higher number of seconds than the time between CDP transmissions, which is set using the cdp timer command.
Examples
In the following example, the CDP packets being sent from the router are configured with a hold time of 60 seconds.
Router(config)#cdp holdtime 60Related Commands
Specifies how often the Cisco IOS software sends CDP updates.
Displays global CDP information, including timer and hold-time information.
cdp log mismatch duplex
To display the log of duplex mismatches generated by the Cisco Discovery Protocol (CDP) on Ethernet interfaces on a router, use the cdp log mismatch duplex command in global configuration or interface configuration mode. To disable the display of duplex messages on all Ethernet interfaces, use the no form of this command.
cdp log mismatch duplex
no cdp log mismatch duplex
Syntax Description
This command has no arguments or keywords.
Defaults
The router reports duplex mismatches from all Ethernet interfaces.
Command Modes
Global configuration
Interface configurationCommand History
Usage Guidelines
When you enter the cdp log mismatch duplex command in global configuration mode, duplex mismatches are displayed on all Ethernet interfaces on the router. When you enter this command in interface configuration mode, only duplex mismatches for the specified Ethernet interface are displayed.
If the cdp log mismatch duplex command is disabled in global configuration mode, it cannot be configured per interface using interface configuration mode.
Duplex mismatch can occur only on Ethernet interfaces.
Examples
The following example of the cdp log mismatch duplex command in global configuration mode enables the display of duplex messages from all Ethernet interfaces on the router:
Router(config)# cdp log mismatch duplexThe following example of the cdp log mismatch duplex command in interface configuration mode enables only the display of duplex messages that may be generated from Ethernet interface 2/1:
Router(config-if)# interface ethernet2/1Router(config-if)# cdp log mismatch duplexThe following is sample output from the show running-config command. The bold text shows that the cdp log mismatch duplex command is disabled globally.
Router# show running-configBuilding configuration...Current configuration : 1395 bytes!version 12.2!hostname 7200_C!!interface Ethernet2/1no ip addressduplex halfno cdp log mismatch duplex!!!!!no cdp log mismatch duplexcdp timer 5!!!!line con 0line aux 0line vty 0 4password labRelated Commands
show running-config
Displays the contents of the currently running configuration file.
cdp run
To enable Cisco Discovery Protocol (CDP), use the cdp run global configuration command. To disable CDP, use the no form of this command.
cdp run
no cdp run
Syntax Description
This command has no arguments or keywords.
Defaults
Enabled
Command Modes
Global configuration
Command History
Usage Guidelines
CDP is enabled on your router by default, which means the Cisco IOS software will receive CDP information. CDP also is enabled on supported interfaces by default. To disable CDP on an interface, use the no cdp enable interface configuration command.
Note
Examples
In the following example, CDP is disabled globally, then the user attempts to enable CDP on the Ethernet 0 interface:
Router(config)#no cdp runRouter(config)#endRouter#show cdp% CDP is not enabledRouter#configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)#int eth0Router(config-if)#cdp enable% Cannot enable CDP on this interface, since CDP is not runningRouter(config-if)#Related Commands
Enables CDP on a supported interface.
Specifies how often the Cisco IOS software sends CDP updates.
router odr
Enables ODR on the hub router.
cdp timer
To specify how often the Cisco IOS software sends Cisco Discovery Protocol (CDP) updates, use the cdp timer global configuration command. To revert to the default setting, use the no form of this command.
cdp timer seconds
no cdp timer
Syntax Description
Defaults
60 seconds
Command Modes
Global configuration
Command History
Usage Guidelines
The trade-off with sending more frequent transmissions is providing up-to-date information versus using bandwidth more often.
Note
Examples
In the following example, CDP updates are sent every 80 seconds, less frequently than the default setting of 60 seconds. You might want to make this change if you are concerned about preserving bandwidth.
cdp timer 80Related Commands
clear cdp counters
To reset Cisco Discovery Protocol (CDP) traffic counters to zero, use the clear cdp counters privileged EXEC command.
clear cdp counters
Syntax Description
This command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
Examples
The following example clears the CDP counters. The show cdp traffic output shows that all of the traffic counters have been reset to zero.
Router# clear cdp countersRouter# show cdp trafficCDP counters:Packets output: 0, Input: 0Hdr syntax: 0, Chksum error: 0, Encaps failed: 0No memory: 0, Invalid packet: 0, Fragmented: 0Related Commands
Clears the table that contains CDP information about neighbors.
Displays traffic information from the CDP table.
clear cdp table
To clear the table that contains Cisco Discovery Protocol (CDP) information about neighbors, use the clear cdp table privileged EXEC command.
clear cdp table
Syntax Description
This command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
Examples
The following example clears the CDP table. The output of the show cdp neighbors command shows that all information has been deleted from the table.
Router# clear cdp tableCDP-AD: Deleted table entry for neon.cisco.com, interface Ethernet0CDP-AD: Deleted table entry for neon.cisco.com, interface Serial0Router# show cdp neighborsCapability Codes: R - Router, T - Trans Bridge, B - Source Route BridgeS - Switch, H - Host, I - IGMPDevice ID Local Intrfce Holdtme Capability Platform Port IDRelated Commands
show cdp
To display global Cisco Discovery Protocol (CDP) information, including timer and hold-time information, use the show cdp privileged EXEC command.
show cdp
Syntax Description
This command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
10.3
This command was introduced.
12.0(3)T
The output of this command was modified to include CDP Version 2 information.
Examples
The following example shows that the current router is sending CDP advertisements every 1 minute (the default setting for the cdp timer global configuration command). Also shown is that the current router directs its neighbors to hold its CDP advertisements for 3 minutes (the default for the cdp holdtime global configuration command), and that the router is enabled to send CDP Version 2 advertisements:
router# show cdpGlobal CDP information:Sending CDP packets every 60 secondsSending a holdtime value of 180 secondsSending CDPv2 advertisements is enabledTable 114 describes the significant fields shown in the display.
Related Commands
show cdp entry
To display information about a specific neighboring device discovered using Cisco Discovery Protocol (CDP), use the show cdp entry privileged EXEC command.
show cdp entry {* | device-name[*] [protocol | version]}
Syntax Description
Command Modes
Privileged EXEC
Command History
Examples
The following is sample output from the show cdp entry command with no limits. Information about the neighbor device.cisco.com is displayed, including device ID, address and protocol, platform, interface, hold time, and version.
Router# show cdp entry device.cisco.com-------------------------Device ID: device.cisco.comEntry address(es):IP address: 192.168.68.18CLNS address: 490001.1111.1111.1111.00DECnet address: 10.1Platform: cisco 4500, Capabilities: RouterInterface: Ethernet0/1, Port ID (outgoing port): Ethernet0Holdtime : 125 secVersion :Cisco IOS SoftwareCisco IOS (tm) 4500 Software (C4500-J-M), Version 12.1(2)Copyright (c) 1986-2000 by cisco Systems, Inc.Compiled Mon 07-Apr-00 19:51 by joeuserThe following is sample output from the show cdp entry protocol command. Only information about the protocols enabled on device.cisco.com is displayed.
Router# show cdp entry device.cisco.com protocolProtocol information for device.cisco.com:IP address: 192.168.68.18CLNS address: 490001.1111.1111.1111.00DECnet address: 10.1The following is sample output from the show cdp entry version command. Only information about the version of software running on device.cisco.com is displayed.
Router# show cdp entry device.cisco.com versionVersion information for device.cisco.com:Cisco IOS SoftwareCisco IOS (tm) 4500 Software (C4500-J-M), Version 12.1(2)Copyright (c) 1986-2000 by cisco Systems, Inc.Compiled Mon 07-Apr-00 19:51 by joeuserRelated Commands
show cdp interface
To display information about the interfaces on which Cisco Discovery Protocol (CDP) is enabled, use the show cdp interface privileged EXEC command.
show cdp interface [type number]
Syntax Description
type
(Optional) Type of interface about which you want information.
number
(Optional) Number of the interface about which you want information.
Command Modes
Privileged EXEC
Command History
Examples
The following is sample output from the show cdp interface command. Status information and information about CDP timer and hold-time settings is displayed for all interfaces on which CDP is enabled.
Router# show cdp interfaceSerial0 is up, line protocol is up, encapsulation is SMDSSending CDP packets every 60 secondsHoldtime is 180 secondsEthernet0 is up, line protocol is up, encapsulation is ARPASending CDP packets every 60 secondsHoldtime is 180 secondsThe following is sample output from the show cdp interface command with an interface specified. Status information and information about CDP timer and hold-time settings is displayed for Ethernet interface 0 only.
Router# show cdp interface ethernet 0Ethernet0 is up, line protocol is up, encapsulation is ARPASending CDP packets every 60 secondsHoldtime is 180 secondsRelated Commands
show cdp neighbors
To display detailed information about neighboring devices discovered using Cisco Discovery Protocol (CDP), use the show cdp neighbors privileged EXEC command.
show cdp neighbors [type number] [detail]
Syntax Description
Command Modes
Privileged EXEC
Command History
10.3
This command was introduced.
12.0(3)T
The output for the detail form of this command was expanded to include CDP Version 2 information.
Examples
The following is sample output for the show cdp neighbors command:
Router#show cdp neighborsCapability Codes: R - Router, T - Trans Bridge, B - Source Route BridgeS - Switch, H - Host, I - IGMP, r - RepeaterDevice ID Local Intrfce Holdtme Capability Platform Port IDlab-7206 Eth 0 157 R 7206VXR Fas 0/0/0lab-as5300-1 Eth 0 163 R AS5300 Fas 0lab-as5300-2 Eth 0 159 R AS5300 Eth 0lab-as5300-3 Eth 0 122 R AS5300 Eth 0lab-as5300-4 Eth 0 132 R AS5300 Fas 0/0lab-3621 Eth 0 140 R S 3631-telcoFas 0/0008024 2758E0 Eth 0 132 T CAT3000 1/2Table 115 describes the fields shown in this example.
The following is sample output for the show cdp neighbors detail command.
router#show cdp neighbors detail-------------------------Device ID: lab-7206Entry address(es):IP address: 172.19.169.83Platform: cisco 7206VXR, Capabilities: RouterInterface: Ethernet0, Port ID (outgoing port): FastEthernet0/0/0Holdtime : 123 secVersion :Cisco Internetwork Operating System SoftwareIOS (tm) 5800 Software (C5800-P4-M), Version 12.1(2)Copyright (c) 1986-2002 by Cisco Systems, Inc.advertisement version: 2Duplex: half-------------------------Device ID: lab-as5300-1Entry address(es):IP address: 172.19.169.87Platform: cisco AS5300, Capabilities: Router--More--...Table 116 describes the fields displayed in the show cdp neighbors output.
Related Commands
show cdp traffic
To display information about traffic between devices gathered using Cisco Discovery Protocol (CDP), use the show cdp traffic privileged EXEC command.
show cdp traffic
Syntax Description
This command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
Examples
The following example specifies information associated with the show cdp traffic command:
router# show cdp trafficTotal packets output: 543, Input: 333Hdr syntax: 0, Chksum error: 0, Encaps failed: 0No memory: 0, Invalid: 0, Fragmented: 0CDP version 1 advertisements output: 191, Input: 187CDP version 2 advertisements output: 352, Input: 146Table 117 describes the significant fields shown in the display.
Related Commands
