LLDP
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). CDP allows network management applications to automatically discover and learn about other Cisco devices connected to the network.
To support non-Cisco devices and to allow for interoperability between other devices, the switch supports the IEEE 802.1AB LLDP. LLDP is a neighbor discovery protocol that is used for network devices to advertise information about themselves to other devices on the network. This protocol runs over the data-link layer, which allows two systems running different network layer protocols to learn about each other.
LLDP supports a set of attributes that it uses to discover neighbor devices. These attributes contain type, length, and value descriptions and are referred to as TLVs. LLDP supported devices can use TLVs to receive and send information to their neighbors. Details such as configuration information, device capabilities, and device identity can be advertised using this protocol.
The switch supports the following basic management TLVs (which are optional):
- Port description TLV
- System name TLV
- System description TLV
- System capabilities TLV
- Management address TLV
- Power Management TLV
These organizationally specific LLDP TLVs are also advertised to support LLDP-MED:
- Port VLAN ID TLV ((IEEE 802.1 specific TLVs)
- MAC/PHY configuration/status TLV(IEEE 802.3 specific TLVs)
LLDP-MED
LLDP for Media Endpoint Devices (LLDP-MED) is an extension to LLDP that operates between endpoint devices such as IP phones and network devices such as switches. It specifically provides support for voice over IP (VoIP) applications and provides additional TLVs for capabilities discovery, network policy, power over Ethernet (PoE), inventory management, and location information. By default, all LLDP-MED TLVs are enabled.
LLDP-MED supports these TLVs:
- LLDP-MED capabilities TLV
Allows LLDP-MED endpoints to determine the capabilities that the connected device supports and what capabilities the device has enabled.
For configuration details, see the For configuration details, see the “Configuring Network-Policy Profile” section.
Allows both network connectivity devices and endpoints to advertise VLAN configurations and associated Layer 2 and Layer 3 attributes for the specific application on that port. For example, the switch can notify a phone of the VLAN number that it should use. The phone can connect into any switch, obtain its VLAN number, and then start communicating with the call control.
By defining a network-policy profile TLV, you can create a profile for voice and voice-signalling by specifying the values for VLAN, class of service (CoS), differentiated services code point (DSCP), and tagging mode. These profile attributes are then maintained centrally on the switch and propagated to the phone.
For configuration details, see the “Configuring Network-Policy Profile” section.
Enables advanced power management between LLDP-MED endpoint and network connectivity devices. Allows switches and phones to convey power information, such as how the device is powered, power priority, and how much power the device needs.
For configuration details, see the “Configuring LLDP Power Negotiation” section.
Allows an endpoint to send detailed inventory information about itself to the switch, including information hardware revision, firmware version, software version, serial number, manufacturer name, model name, and asset ID TLV.
Provides location information from the switch to the endpoint device. The location TLV can send this information:
– Civic location information
Provides the civic address information and postal information. Examples of civic location information are street address, road name, and postal community name information.
– ELIN location information
Provides the location information for a caller. The location is determined by the emergency location identifier number (ELIN), which is a phone number that routes an emergency call to the local public safety answering point (PSAP) and which the PSAP can use to call back the emergency caller.
For configuration details, see the “Configuring Location TLV and Location Service” section.
Note A switch cannot send LLDP and LLDP-MED simultaneously to an end-point device. By default, a network device sends only LLDP packets until it receives LLDP-MED packets from an end-point device. The network device then sends LLDP-MED packets until it receives only LLDP packets.
Location Service
The location service feature enables the switch to provide location and attachment tracking information for its connected devices to a Cisco Mobility Services Engine (MSE). The tracked device can be a wireless endpoint, a wired endpoint, or a wired switch or controller. The switch informs device link up and link-down events through Network Mobility Services Protocol (NMSP) location and attachment notifications to the MSE.
The MSE initiates the NMSP connection to the switch. When the MSE connects to the switch messages are exchanged to establish version compatibility, service exchange, and location information synchronization. After the connection is established, the switch sends location and attachment notifications periodically to the MSE. Any link-up event, link-down event, or location configuration change detected during the interval are aggregated and sent at the end of the interval using attachment or location notifications.
When the switch discovers the presence or absence of a device on a link-up or link-down event on a port, it obtains the client’s MAC address, IP address, and 802.1x username if applicable. If the device is LLDP-MED or CDP enabled, the switch continues to gather client-specific information such as the model number and software version.
Depending on the device capabilities, the switch obtains this client attachment information at link up:
- Slot, port, and port-type
- Client’s MAC address
- Client’s IP address
- 802.1X username if applicable
- Device category is specified as a wired station
- State is specified as Connected
- Serial number, UDI
- Model number
- Software version
- VLAN ID and VLAN name
Depending on the device capabilities, the switch obtains this client information at link down:
- Slot and port that was disconnected
- Client’s MAC address
- Client’s IP address
- 802.1X username if applicable
- Device category is specified as a wired station
- State is specified as Disconnected
- Serial number, UDI
- Model number
- Software version
- VLAN ID and VLAN name
If an administrator changes a location address at the switch, the information is reported to the MSE. The switch sends a NMSP location notification message that identifies the list of ports affected by the change and the changed address information.