- Preface
- Software Licensing
- The Cisco IOS command-line interface (CLI)
- Configuring Interfaces
- Switch Alarms
- Initial Switch Configuration (IP address assignments and DHCP autoconfiguration)
- How to Setup and Use the Cisco Configuration Engine
- How to Create and Manage Switch Clusters
- Performing Switch Administration
- Configuring Precision Time Protocol (PTP)
- Configuring PROFINET
- Common Industrial Protocol (CIP)
- Configuring SDM Templates
- Configuring Switch-Based Authentication
- Configuring IEEE 802.1x Port-Based Authentication
- MACsec
- Web-Based Authentication
- Configuring Smartports Macros
- Configuring SGACL Monitor Mode and SGACL Logging
- Configuring SGT Exchange Protocol over TCP (SXP) and Layer 3 Transport
- Configuring VLANs
- VLAN Trunking Protocol (VTP)
- Configuring Voice VLAN
- How to Configure Spanning Tree Protocol (STP)
- Configuring MSTP
- Configuring Optional Spanning-Tree Features
- Configuring Resilient Ethernet Protocol
- Configuring the FlexLinks and the MAC Address-Table Move Update
- Configuring DHCP
- Dynamic Address Resolution Protocol (ARP)
- Configuring IP Source Guard
- How to Configure Internet Group Management Protocol (IGMP) and Multicast VLAN Registration (MVR)
- Configuring Port-Based Traffic Control
- Configuring LLDP, LLDP-MED, and Wired Location Service
- Configuring SPAN and RSPAN
- One-to-one (1:1) Layer 2 Network Address Translation (NAT)
- How to Configure CDP
- Configuring UniDirectional Link Detection (UDLD)
- Configuring RMON
- Configuring System Message Logging
- Configuring Simple Network Management Protocol (SNMP)
- Network Security with ACLs
- Configuring Quality of Service (QoS)
- Configuring Static IP Unicast Routing
- Configuring IPv6 Host Functions
- Configuring Link State Tracking
- Configuring IP multicast routing
- Configuring Multicast Source Discovery Protocol (MSDP)
- Configuring Multicast Listener Discovery (MLD) snooping
- Configuring HSRP and VRRP
- Configuring IPv6 access control lists (ACLs)
- Configuring Embedded Event Manager (EEM)
- IP Unicast Routing
- IPv6 Unicast Routing
- Unicast Routing Overview
- Configuring Cisco IOS IP SLAs Operations
- Configuring Dying-Gasp
- How to Configure Enhanced Object Tracking
- Configuring MODBUS TCP
- Configuring Ethernet CFM
- Working with the Flash File System
- How to Configure EtherChannels
- Troubleshooting
- How to use a Secure Digital (SD) flash memory module (SD card)
Configuring CDP
Information About CDP
CDP
CDP is a device discovery protocol that runs over Layer 2 (the data link layer) on all Cisco-manufactured devices (routers, bridges, access servers, and switches) and allows network management applications to discover Cisco devices that are neighbors of already known devices. With CDP, network management applications can learn the device type and the Simple Network Management Protocol (SNMP) agent address of neighboring devices running lower-layer, transparent protocols. This feature enables applications to send SNMP queries to neighboring devices.
CDP runs on all media that support Subnetwork Access Protocol (SNAP). Because CDP runs over the data-link layer only, two systems that support different network-layer protocols can learn about each other.
Each CDP-configured device sends periodic messages to a multicast address, advertising at least one address at which it can receive SNMP messages. The advertisements also contain time-to-live, or holdtime information, which is the length of time a receiving device holds CDP information before discarding it. Each device also listens to the messages sent by other devices to learn about neighboring devices.
On the switch, CDP enables Network Assistant to display a graphical view of the network. The switch uses CDP to find cluster candidates and maintain information about cluster members and other devices up to three cluster-enabled devices away from the command switch by default.
For a switch and connected endpoint devices running Cisco Medianet, these events occur:
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CDP identifies connected endpoints that communicate directly with the switch.
■Only one wired switch reports the location information to prevent duplicate reports of neighboring devices.
■The wired switch and the endpoints both send and receive location information.
■The SDM template for IE 5000 should have the log keyword if extended ACL matches are to be displayed for the permit statement. An extended ACL's permit statement will not show matches if the SDM template is set to default.
Default CDP Configuration
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How to Configure CDP
Configuring the CDP Parameters
You can configure the frequency of CDP updates, the amount of time to hold the information before discarding it, and whether or not to send Version-2 advertisements.
Note: Steps 2 through 4 are all optional and can be performed in any order.
Disabling CDP
Note: Switch clusters and other Cisco devices (such as Cisco IP Phones) regularly exchange CDP messages. Disabling CDP can interrupt cluster discovery and device connectivity.
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Specifies the interface on which you are disabling CDP, and enters interface configuration mode. |
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Monitoring and Maintaining CDP
Configuration Examples for CDP
Configuring CDP Parameters: Example
This example shows how to configure CDP parameters:
Enabling CDP: Examples
This example shows how to enable CDP on a port when it has been disabled:
Note: Voice VLAN is not counted against port security when CDP is disabled on the switch interface.
This example shows how to enable CDP if it has been disabled:
Additional References
The following sections provide references related to switch administration:
Related Documents
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Cisco IOS basic commands |
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Standards
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No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
MIBs
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To locate and download MIBs using Cisco IOS XR software, use the Cisco MIB Locator found at the following URL and choose a platform under the Cisco Access Products menu: http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml |
RFCs
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No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature. |
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