Cisco Discovery Protocol - Cisco ASR 900 Series Configuration Manual

TLV
Native VLAN TLV
Platform TLV
Port-ID TLV
Version TLV
VTP Management Domain TLV

Cisco Discovery Protocol

Cisco Discovery Protocol is a Layer 2, media-independent, and network-independent protocol that networking applications use to
learn about nearby, directly connected devices. Cisco Discovery Protocol is enabled by default. Each device configured for Cisco
Discovery Protocol advertises at least one address at which the device can receive messages and sends periodic advertisements
(messages) to the well-known multicast address 01:00:0C:CC:CC:CC. Devices discover each other by listening at that address. They
also listen to messages to learn when interfaces on other devices are up or go down.
Advertisements contain time-to-live information, which indicates the length of time a receiving device should hold Cisco Discovery
Protocol information before discarding it. Advertisements supported and configured in Cisco software are sent, by default, every 60
seconds on interfaces that support Subnetwork Access Protocol (SNAP) headers. Cisco devices never forward Cisco Discovery
Protocol packets. Cisco devices that support Cisco Discovery Protocol store the information received in a table. Information in this
table is refreshed every time an advertisement is received, and information about a device is discarded after three advertisements
from that device are missed.
The information contained in Cisco Discovery Protocol advertisements varies based on the type of device and the installed version
of the operating system. Some of the information that Cisco Discovery Protocol can learn includes:
• Cisco IOS version running on Cisco devices
• Hardware platform of devices
• IP addresses of interfaces on devices
• Locally connected devices advertising Cisco Discovery Protocol
• Interfaces active on Cisco devices, including encapsulation type
• Hostname
• Duplex setting
• VLAN Trunking Protocol (VTP) domain
• Native VLAN
4
Definition
Indicates, per interface, the assumed VLAN for untagged packets on the interface.
Cisco Discovery Protocol learns the native VLAN for an interface.
This field is implemented only for interfaces that support the IEEE 802.1Q
protocol.
Identifies the hardware platform of the device. For example, Cisco 4500.
Identifies the port on which a Cisco Discovery Protocol packet is sent.
Contains the device software release information.
Advertises the configured VLAN Trunking Protocol (VTP)-management-domain
name of the system. This name is used by network operators to verify
VTP-domain configuration in adjacent network nodes.