Руководство по настройке Cisco Discovery Protocol для коммутаторов Catalyst 2960 (PDF)

Cisco Discovery Protocol Overview

Configuring Cisco Discovery Protocol Cisco Discovery Protocol is a Layer 2, media-independent, and network-independent protocol that runs on Cisco devices and enables networking applications to learn about directly connected devices nearby. This protocol facilitates the management of Cisco devices by discovering these devices, determining how they are configured, and allowing systems using different network-layer protocols to learn about each other. This module describes Cisco Discovery Protocol Version 2 and how it functions with SNMP.

Information about Cisco Discovery Protocol, on page 1 How to Configure Cisco Discovery Protocol, on page 2 Monitoring and Maintaining Cisco Discovery Protocol, on page 8 Feature History for Cisco Discovery Protocol, on page 9 Information about Cisco Discovery Protocol The following sections provide information about Cisco Discovery Protocol Default Cisco Discovery Protocol Configuration This table shows the default Cisco Discovery Protocol configuration.

Cisco Discovery Protocol Overview Cisco Discovery Protocol is a device discovery protocol that runs over Layer 2 (the data-link layer) on all Cisco-manufactured devices (routers, bridges, access servers, controllers, and switches) and allows network management applications to discover Cisco devices that are neighbors of already known devices.

With Cisco Configuring Cisco Discovery Protocol Feature Default Setting Cisco Discovery Protocol global state Enabled Cisco Discovery Protocol interface state Enabled Cisco Discovery Protocol timer (packet update frequency) 60 seconds Cisco Discovery Protocol holdtime (before discarding) 180 seconds Cisco Discovery Protocol Version-2 advertisements Enabled 1

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Configuring Cisco Discovery Protocol Characteristics

Discovery Protocol, network management applications can learn the device type and the SNMP agent address of neighboring devices running lower-layer, transparent protocols. This feature enables applications to send SNMP queries to neighboring devices. Cisco Discovery Protocol runs on all media that support Subnetwork Access Protocol (SNAP). Because Cisco Discovery Protocol runs over the data-link layer only, two systems that support different network-layer protocols can learn about each other. Each Cisco Discovery Protocol-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 Cisco Discovery Protocol information before discarding it. Each device also listens to the messages sent by other devices to learn about neighboring devices. On the device, Cisco Discovery Protocol enables Network Assistant to display a graphical view of the network. The device uses Cisco Discovery Protocol to find cluster candidates and maintain information about cluster members and other devices up to three cluster-enabled devices away from the command device by default. The following applies to a device and connected endpoint devices:

• Cisco Discovery Protocol identifies connected endpoints that communicate directly with the device. • To prevent duplicate reports of neighboring devices, only one wired device reports the location information. • The wired device and the endpoints both send and receive location information. How to Configure Cisco Discovery Protocol The following sections provide information about how to configure Cisco Discovery Protocol. Configuring Cisco Discovery Protocol Characteristics You can configure these Cisco Discovery Protocol characteristics:

• Frequency of Cisco Discovery Protocol updates • Amount of time to hold the information before discarding it • Whether or not to send Version 2 advertisements Steps 3 through 5 are all optional and can be performed in any order. Note Follow these steps to configure the Cisco Discovery Protocol characteristics. Procedure Configuring Cisco Discovery Protocol How to Configure Cisco Discovery Protocol Command or Action Purpose Step 1 enable Example: Enables privileged EXEC mode. • Enter your password if prompted. Configuring Cisco Discovery Protocol 2

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Configuring Cisco Discovery Protocol Characteristics

What to do next Use the no form of the Cisco Discovery Protocol commands to return to the default settings. Configuring Cisco Discovery Protocol Configuring Cisco Discovery Protocol Characteristics Command or Action Purpose Device>enable Step 2 configure terminal Example: Device# configure terminal Step 3 cdp timer seconds Example: Device(config)# cdp timer 20 (Optional) Sets the transmission frequency of Cisco Discovery Protocol updates in seconds. The range is 5 to 254; the default is 60 seconds. Step 4 cdp holdtime seconds Example:

Device(config)# cdp holdtime 60 (Optional) Specifies the amount of time a receiving device should hold the information sent by your device before discarding it. The range is 10 to 255 seconds; the default is 180 seconds. Step 5 cdp advertise-v2 Example: Device(config)# cdp advertise-v2 (Optional) Configures Cisco Discovery Protocol to send Version 2 advertisements. This is the default state. Step 6 end Example: Device(config)# end Returns to privileged EXEC mode. Step 7 show running-config Example: Device# show running-config Verifies your entries. Step 8 copy running-config startup-config Example:

Device# copy running-config startup-config (Optional) Saves your entries in the configuration file. Configuring Cisco Discovery Protocol 3

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Disabling Cisco Discovery Protocol

Disabling Cisco Discovery Protocol Cisco Discovery Protocol is enabled by default. Device clusters and other Cisco devices (such as Cisco IP Phones) regularly exchange Cisco Discovery Protocol messages. Disabling Cisco Discovery Protocol can interrupt cluster discovery and device connectivity. Note Follow these steps to disable the Cisco Discovery Protocol device discovery capability. Procedure Configuring Cisco Discovery Protocol Disabling Cisco Discovery Protocol Command or Action Purpose Step 1 enable Example: Device>enable Enables privileged EXEC mode. • Enter your password if prompted. Step 2 configure terminal Example: Device# configure terminal Enters global configuration mode.

Step 3 no cdp run Example: Device(config)# no cdp run Disables Cisco Discovery Protocol. Step 4 end Example: Device(config)# end Returns to privileged EXEC mode. Step 5 show running-config Example: Device# show running-config Verifies your entries. Step 6 copy running-config startup-config Example: Device# copy running-config startup-config (Optional) Saves your entries in the configuration file. Configuring Cisco Discovery Protocol 4

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