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CDP / LLDPGlobal Config

no cdp run

Globally disables Cisco Discovery Protocol (CDP) on the router or switch to prevent device discovery and reduce unnecessary traffic.

Syntax·Global Config
no cdp run

When to Use This Command

  • Disabling CDP on a router connected to an untrusted network to prevent information leakage.
  • Disabling CDP globally on a switch in a secure environment where device discovery is not required.
  • Troubleshooting network issues by eliminating CDP-related traffic to isolate problems.
  • Complying with security policies that prohibit the use of discovery protocols.

Command Examples

Disabling CDP globally

Router(config)# no cdp run
Router(config)#

The command is entered in global configuration mode. No output is displayed upon successful execution; the prompt returns without error.

Verifying CDP is disabled

Router# show cdp
Global CDP information:
	Sending CDP packets every 60 seconds
	Sending a holdtime value of 180 seconds
	Sending CDPv2 advertisements is enabled
CDP is not enabled on any interfaces.

The output shows CDP global parameters but indicates 'CDP is not enabled on any interfaces' because the 'no cdp run' command disables CDP globally, overriding any per-interface enablement.

Understanding the Output

The 'no cdp run' command does not produce any output on success. To verify CDP status, use 'show cdp'. The output displays global CDP parameters such as packet interval (default 60 seconds), holdtime (default 180 seconds), and CDP version (v2). The key line is 'CDP is not enabled on any interfaces', which confirms that CDP is disabled globally. If CDP were enabled, the output would list interfaces with CDP active. A common mistake is to assume CDP is off based on the absence of interface output, but the global parameters still appear; the critical indicator is the last line.

CCNA Exam Tips

1.

CCNA exam tip: 'no cdp run' disables CDP globally, while 'no cdp enable' disables it per interface. Know the difference.

2.

CCNA exam tip: CDP is enabled by default on Cisco devices. You may need to disable it for security reasons in exam scenarios.

3.

CCNA exam tip: After disabling CDP globally, you cannot enable it on individual interfaces; the global setting overrides.

4.

CCNA exam tip: Use 'show cdp neighbors' to see neighbors; if CDP is disabled, the command returns no output.

Common Mistakes

Mistake 1: Using 'no cdp enable' instead of 'no cdp run' to disable globally — 'no cdp enable' only disables on the current interface.

Mistake 2: Forgetting to save the configuration after disabling CDP — the change is lost on reload if not saved.

Mistake 3: Assuming CDP is disabled because 'show cdp neighbors' shows nothing — CDP might be enabled but no neighbors discovered.

Related Commands

cdp enable

Enables Cisco Discovery Protocol (CDP) on a specific interface to allow the device to advertise itself and discover neighboring Cisco devices.

cdp run

Enables Cisco Discovery Protocol (CDP) globally on the device to discover directly connected Cisco devices and gather information about them.

show cdp neighbors

Displays information about directly connected Cisco devices discovered via CDP, used to verify neighbor relationships and gather device details.

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