Specifications

CHAPTER
27-1
Cisco MWR 2941 Mobile Wireless Edge Router Release 3.5 Software Configuration Guide, Cisco IOS Release 15.1(3)MR
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27
Configuring Cisco Discovery Protocol
This chapter describes how to configure Cisco Discovery Protocol (CDP) on the Cisco MWR 2941
router.
Note For complete syntax and usage information for the commands used in this chapter, see the Cisco MWR
2941 Mobile Wireless Edge Router IOS Command Reference, Release 15.0(1)MR and the Configuration
Fundamentals Configuration Guide, Cisco IOS Release 15.0S.
Note The Cisco MWR 2941 does not necessarily support all of the commands described in the Release
15.0(1)S documentation.
• Understanding CDP, page 27-1
• Configuring CDP, page 27-2
• Monitoring and Maintaining CDP, page 27-5
Understanding 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.