Information Technology Reference
In-Depth Information
ID, address, port ID, capabilities, version, platform, and native VLAN, with much of the information being represented in an ASCII
format.
CDP messages are made up of Version, Time to Live (TTL), and Checksum fields, followed by a number of Type, Length, Values
(TLV). These TLVs can include the following:
Device-ID (type 0x0001): This identifies the sending device.
Address (0x0002): The address of the interface sending the CDP update.
Port-ID (0x0003): The port from which the CDP update is sent.
Capabilities (0x0004): Device's functional capabilities (for example, whether it is a router or switch).
Version (0x0005): Software version running on the device.
Platform (0x0006): The hardware platform.
VTP Domain (0x0009): The VTP domain.
Native VLAN (0x000a): The 802.1Q native VLAN.
Appliance VLAN-ID (0x000e): This contains one or more tuples. Each of these contains an appliance ID and a VLAN ID.
Power Consumption (0x0010): This indicates the maximum amount of power (milliwatts) that the device expects.
Extended Trust (0x0012): This indicates to a device, such as a Cisco IP phone, that the QoS trust should be extended to the
PC port of the IP phone.
CoS for Untrusted Ports (0x0013): Specifies the CoS value that a device, such as a Cisco IP phone, should mark packets
received on an untrusted port with.
By default, Cisco IP phones mark voice media frames with CoS(802.1p)/DSCP of 5/EF and call signaling frames with
CoS(802.1p)/DSCP of 3/AF31 or CS3.
 
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