To support non-Cisco devices and to allow for interoperability between other devices, the Cisco NCS 4000 Series Router 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 also allows NCS 4000 devices to discover information about its peer devices connected through the OTN ports and the packet interfaces. This protocol runs over the Data Link Layer, which allows two systems running different network layer protocols to learn about each other. The feature is supported on client ports of the NCS4K-4H-OPW-QC2 card that support Ethernet-over-OTN configuration and the packet interfaces.

LLDP supports a set of attributes that it uses to learn information about neighbor devices. These attributes have a defined format known as a Type-Length-Value (TLV). 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.

In addition to the mandatory TLVs (Chassis ID, Port ID, and Time-to-Live), the router also supports the following basic management TLVs, which are optional:

• Port Description

• System Name

• System Description

• System Capabilities

• Management Address

These optional TLVs are automatically sent when LLDP is active, but you can disable them as needed using the lldp tlv-select disable command.

LLDP frames use the IEEE 802.3 format, which consists of the following fields:

• Destination address (6 bytes)—Uses a multicast address of 01-80-C2-00-00-0E.

• Source address (6 bytes)—MAC address of the sending device or port.

• LLDP Ethertype (2 bytes)—Uses 88-CC.

• LLDP PDU (1500 bytes)—LLDP payload consisting of TLVs.

• FCS (4 bytes)—Cyclic Redundancy Check (CRC) for error checking.

LLDP is a one-way protocol. The basic operation of LLDP consists of a device enabled for transmit of LLDP information sending periodic advertisements of information in LLDP frames to a receiving device.

Devices are identified using a combination of the Chassis ID and Port ID TLVs to create an MSAP (MAC Service Access Point). The receiving device saves the information about a neighbor for a certain amount time specified in the TTL TLV, before aging and removing the information.

LLDP supports the following additional operational characteristics:

• LLDP can operate independently in transmit or receive modes.

• LLDP operates as a slow protocol using only untagged frames, with transmission speeds of less than 5 frames per second.

• LLDP packets are sent when the following occurs:

  • The packet update frequency specified by the lldp timer command is reached. The default is 30 seconds.

  • When a change in the values of the managed objects occurs from the local system's LLDP MIB.

  • When LLDP is activated on an interface (3 frames are sent upon activation).

• When an LLDP frame is received, the LLDP remote services and PTOPO MIBs are updated with the information in the TLVs.

• LLDP supports the following actions on these TLV characteristics:

  • Interprets a TTL value of 0 as a request to automatically purge the information of the transmitting device. These shutdown LLDPDUs are typically sent prior to a port becoming inoperable.

  • An LLDP frame with a malformed mandatory TLV is dropped.

  • A TLV with an invalid value is ignored.

  • A copy of an unknown organizationally-specific TLV is maintained if the TTL is non-zero, for later access through network management.

The Cisco NCS 4000 Series Router supports the following LLDP functions:

• IPv4 management addresses—In general, IPv4 addresses will be advertised if they are available, and preference is given to the address that is configured on the transmitting interface.

  If the transmitting interface does not have a configured address, then the TLV will be populated with an address from another interface. The advertised LLDP IP address is implemented according to the following priority order of IP addresses for interfaces on the Cisco NCS 4000 Series Router:

  • Locally configured address

  • MgmtEth0/RP0/CPU0/0

  • MgmtEth0/RP0/CPU0/1

  • MgmtEth0/RP1/CPU0/0

  • MgmtEth0/RP1/CPU0/1

  • Loopback interfaces

• LLDP is supported for the nearest physically attached, non-tunneled neighbors.

• Port ID TLVs are supported for Ethernet interfaces, subinterfaces, bundle interfaces, and bundle subinterfaces.

The following LLDP functions are not supported on the Cisco NCS 4000 Series Router:

• LLDP-MED organizationally unique extension—However, interoperability still exists between other devices that do support this extension.

• Tunneled neighbors, or neighbors more than one hop away.

• LLDP TLVs cannot be disabled on a per-interface basis; However, certain optional TLVs can be disabled globally.

• LLDP SNMP trap lldpRemTablesChange.

This section includes the procedures for configuring LLDP.