Cisco Systems N3KC3048TP1GE About Interface Speed, About the Cisco Discovery Protocol, Feature

Configuring Ethernet Interfaces

About Interface Speed

In these cases, the UDLD aggressive mode disables one of the ports on the link, which prevents traffic from being discarded.

About Interface Speed

A Cisco Nexus 3000 Series switch has a number of fixed 10-Gigabit ports, each equipped with SFP+ interface adapters.

About the Cisco Discovery Protocol

The Cisco Discovery Protocol (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.

The switch supports both CDP Version 1 and Version 2.

Default CDP Configuration

The following table shows the default CDP configuration.

Table 3: Default CDP Configuration
Feature	Default Setting
CDP interface state	Enabled
CDP timer (packet update frequency)	60 seconds
CDP holdtime (before discarding)	180 seconds
CDP Version-2 advertisements	Enabled

About the Error-Disabled State

An interface is in the error-disabled (err-disabled) state when the inteface is enabled administratively (using the no shutdown command) but disabled at runtime by any process. For example, if UDLD detects a unidirectional link, the interface is shut down at runtime. However, because the interface is administratively

	Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
10	OL-26590-01