Cisco NCS 5000 Series Manual page 68

Information About Implementing CDP
contain time-to-live, or hold-time, information, which indicates the length of time a receiving device holds
CDP information before discarding it. Each device also listens to the periodic CDP messages sent by others
to learn about neighboring devices and determine when their interfaces to the media go up or down.
CDP Version-2 (CDPv2) is the most recent release of the protocol and provides more intelligent device
tracking features. These features include a reporting mechanism that allows for more rapid error tracking,
thereby reducing costly downtime. Reported error messages can be sent to the console or to a logging server,
and can cover instances of unmatching native VLAN IDs (IEEE 802.1Q) on connecting ports, and unmatching
port duplex states between connecting devices.
CDPv2 show commands can provide detailed output on VLAN Trunking Protocol (VTP) management
domain and duplex modes of neighbor devices, CDP-related counters, and VLAN IDs of connecting ports.
Type-length-value fields (TLVs) are blocks of information embedded in CDP advertisements.
Type-Length-Value Definitions for CDPv2, on page 58
advertisements.
Table 5: Type-Length-Value Definitions for CDPv2
TLV
Device-ID TLV
Address TLV
Port-ID TLV
Capabilities TLV
Version TLV
Platform TLV
VTP Management Domain TLV
Native VLAN TLV
Full/Half Duplex TLV
System Management Configuration Guide for Cisco NCS 5000 Series Routers, IOS XR Release 6.2.x
58
summarizes the TLV definitions for CDP
Definition
Identifies the device name in the form of a character string.
Contains a list of network addresses of both receiving and sending
devices.
Identifies the port on which the CDP packet is sent.
Describes the functional capability for the device in the form of a
device type; for example, a switch.
Contains information about the software release version on which the
device is running.
Describes the hardware platform name of the device, for example,
Cisco 4500.
Advertises the system's configured VTP management domain
name-string. Used by network operators to verify VTP domain
configuration in adjacent network nodes.
Indicates, per interface, the assumed VLAN for untagged packets on
the interface. CDP learns the native VLAN for an interface. This
feature is implemented only for interfaces that support the
IEEE 802.1Q protocol.
Indicates status (duplex configuration) of CDP broadcast interface.
Used by network operators to diagnose connectivity problems between
adjacent network elements.
Implementing CDP
Table 5: