LLDP
This help contains the following topics:
Introduction
The Link Layer Discovery Protocol (LLDP) is a standard link layer protocol. In an LLDP-enabled network, a device contains its information in a TLV which is an information element that contains the type, length, and value fields and advertises local device information in LLDP Data Units (LLDPDUs) to the directly connected devices. The information distributed through LLDP is stored by its recipients in standard MIBs, making it possible for the information to be accessed by a Network Management System (NMS) through SNMP.
Information that can be distributed through LLDP includes (but is not limited to):
Major capabilities of the system.
Management IP address of the system.
Device ID.
Port ID.
Application scenarios
LLDP is typically used for device discovery in multi-vendor network. It enables network devices to discover the identity and capabilities of each other and how they are connected through broadcasting. LLDP is mainly applied in the following application scenarios:
Network discovery and mapping: You can use LLDP to identify devices and their connections on a network. This is useful for creating and maintaining the network topology.
Troubleshooting: When a network issue occurs, LLDP can help quickly locate the issue since it provides connectivity information between devices.
Configuration verification: LLDP can be used to verify that network configurations are operating as expected, for example, ensuring that switch ports are connected to the correct access points.
Asset management: LLDP can help track the locations and states of all devices on a network, which is crucial for asset management.
Auto configuration: Some network devices might use LLDP information for automated configuration, such as automatic assignment of voice VLANs.
Network security: LLDP can help identify unauthorized devices on a network, which is crucial for ensuring network security.
System integration: LLDP can help integrate devices from different vendors on a complex network to ensure that these devices can identify each other and collaborate effectively.
Data center management: In large-scale data centers, LLDP can manage a large number of switches, servers, and other network devices, providing efficient network management capabilities.
Voice and video networks: On voice and video networks, LLDP can help identify endpoint devices and configure the network correctly to ensure the correct operation of QoS.
Restrictions and guidelines
When you enable LLDP, follow these restrictions and guidelines:
For LLDP to take effect on a port, you must enable LLDP both globally and on the port.
To use LLDP together with OpenFlow, you must enable LLDP globally on OpenFlow switches. To prevent LLDP from affecting topology discovery of OpenFlow controllers, disable LLDP on ports of OpenFlow instances.
You can configure LLDP on an IRF physical interface to monitor the connection and link status of the IRF physical link. An LLDP-enabled IRF physical interface supports only the nearest bridge agent.
For transparent transmission of LLDP frames in an EVPN-capable M-LAG system, if the evpn m-lag local command is executed on an M-LAG member device, the remote peer will forward multiple LLDP frames to the M-LAG member device. To resolve this issue, you can execute the undo evpn m-lag local command on the M-LAG member device. Identify whether the undo evpn m-lag local command can be executed according to networking requirements.
Configuration guide
Analysis
Configure LLDP as shown in the following figure:
Basic configuration
Select Network Config > More > LLDP.
Select whether to enable LLDP globally in the Global LLDP field.
On the Interface Configuration tab, you can enable for a single interface or interfaces in bulk.
To refresh the interface configuration information, click Refresh.
Enable LLDP for a single interface
On the Interface Configuration tab, select the target interface and enable Interface LLDP in the Basic Configuration area. Then, click Submit.
Enable LLDP for interfaces in bulk
On the Interface Configuration tab, select interfaces in bulk, click Bulk Operation, and then select Batch Enable LLDP. You can also perform other operations in bulk. For more information about the parameters, see Table-1.
Table-1 Parameters for configuring interfaces in bulk
Parameter
Description
Batch Enable LLDP
Enable LLDP for interfaces in bulk.
Batch Disable LLDP
Disable LLDP for interfaces in bulk.
Batch Restore Default Values
Disable the default configuration for interfaces in bulk.
To export interface configuration to the local, click More and select Export.
On the LLDP Neighbor tab, you can click Refresh to refresh the LLDP neighbor information for the device.
Advanced configuration
Select Network Config > More > LLDP > Global Configuration. In the Advanced Configuration area, configure the parameters as shown in Table-2. Click Submit.
Table-2 Parameters for configuring global advanced settings
Parameter
Description
Global Compatible CDP
When the device is directly connected to a Cisco device that supports only Cisco Discovery Protocol (CDP) and does not support LLDP, you can configure the CDP-compatible LLDP feature to interact With the directly connected device.
LLDP Bridge Mode
When LLDP operates in customer bridge mode, LLDP supports nearest bridge agent, nearest non-TPMR bridge agent, and nearest customer bridge agent. When LLDP operates in service bridge mode, LLDP supports nearest bridge agent and nearest non-TPMR bridge agent.
TTL (LLDP Aging Time)
The Time to Live TLV carried in an LLDPDU determines how long the device information carried in the LLDPDU can be saved on a recipient device.
By setting the TTL multiplier, you can configure the TTL of locally sent LLDPDUs. The TTL is expressed by using the following formula:
TTL = Min (65535, (TTL multiplier × LLDP frame transmission interval + 1))
As the expression shows, the TTL can be up to 65535 seconds. TTLs greater than 65535 will be rounded down to 65535 seconds.
When you configure CDP compatibility for LLDP, the maximum TTL value that CDP allows is 255 seconds. To make CDP-compatible LLDP work correctly with Cisco IP phones, configure the LLDP frame transmission interval to be no more than 1/3 of the TTL value.
Message Sending Time Interval
An LLDP agent operating in TxRx mode or Tx mode sends LLDP frames to its directly connected devices periodically.
Multiplier
The Time to Live TLV carried in an LLDPDU determines how long the device information carried in the LLDPDU can be saved on a recipient device.
By setting the TTL multiplier, you can configure the TTL of locally sent LLDPDUs. The TTL is expressed by using the following formula:
TTL = Min (65535, (TTL multiplier × LLDP frame transmission interval + 1))
As the expression shows, the TTL can be up to 65535 seconds. TTLs greater than 65535 will be rounded down to 65535 seconds.
LLDP Message Reception Timeout Detection
If an interface has not received any frames when the timeout timer expires, the device reports a no LLDP neighbor event to the NETCONF module. This feature can detect only directly connected LLDP neighbors. To avoid misdetection, make sure the timeout for receiving LLDP frames is greater than the LLDP frame transmission interval.
LLDP PVID Inconsistency Check
When the device is directly connected to a Cisco device that supports only Cisco Discovery Protocol (CDP) and does not support LLDP, you can configure the CDP-compatible LLDP feature to interact With the directly connected device.
Token Bucket Size Limiting Message Sending Rate
To prevent the frequent changes of local information from causing a large amount of LLDP message sending, the token bucket mechanism is used to limit the speed of LLDP message sending.
Fast Sending Message Time Interval
LLDP automatically enables the fast LLDP frame transmission mechanism in either of the following cases:
A new LLDP frame is received and carries device information new to the local device.
The LLDP operating mode of the LLDP agent changes from Disable or Rx to TxRx or Tx.
The fast LLDP frame transmission mechanism successively sends the specified number of LLDP frames at a configurable fast LLDP frame transmission interval. The mechanism helps LLDP neighbors discover the local device as soon as possible. Then, the normal LLDP frame transmission interval resumes.
Number of Fast Sending LLDP Messages
LLDP automatically enables the fast LLDP frame transmission mechanism in either of the following cases:
A new LLDP frame is received and carries device information new to the local device.
The LLDP operating mode of the LLDP agent changes from Disable or Rx to TxRx or Tx.
The fast LLDP frame transmission mechanism successively sends the specified number of LLDP frames at a configurable fast LLDP frame transmission interval. The mechanism helps LLDP neighbors discover the local device as soon as possible. Then, the normal LLDP frame transmission interval resumes.
Trap Information Sending Time Interval
Specify the minimum time interval for the device to send traps to the network management system. This configuration takes effect only when LLDP trapping is enabled for an interface.
Interface Initialization Delay Time
When the LLDP operating mode on an interface changes, the interface will initialize the protocol state machine. This configuration can avoid frequent interface initialization caused by frequent changes of the LLDP operating mode,
Select Network Config > More > LLDP > Interface Configuration. In the Advanced Configuration area, configure the parameters as shown in Table-3. Click Submit.
Table-3 Parameters for configuring interface advanced settings
Parameter
Description
Operating Mode of Nearest Bridge Agent
By default, the nearest bridge agent operates in RxTx mode. The following operating modes are available:
Disable: Specifies the Disable mode. A port in this mode cannot send or receive LLDP frames.
Tx: Specifies the Tx mode. A port in this mode can only send LLDP frames.
Rx: Specifies the Rx mode. A port in this mode can only receive LLDP frames.
Operating Mode of Nearest Non-TPMR Bridge Agent
By default, the nearest non-TPMR bridge agent operates in Disable mode. The following operating modes are available:
TxRx: Specifies the TxRx mode. A port in this mode can send and receive LLDP frames.
Tx: Specifies the Tx mode. A port in this mode can only send LLDP frames.
Rx: Specifies the Rx mode. A port in this mode can only receive LLDP frames.
Operating Mode of Nearest Customer Bridge Mode
By default, the nearest customer bridge agent operates in Disable mode. The following operating modes are available:
TxRx: Specifies the TxRx mode. A port in this mode can send and receive LLDP frames.
Tx: Specifies the Tx mode. A port in this mode can only send LLDP frames.
Rx: Specifies the Rx mode. A port in this mode can only receive LLDP frames.
Message Encapsulation Format of Nearest Bridge Agent
By default, LLDP frames are encapsulated in Ethernet format. LLDP-CDP packets use only SNAP encapsulation.
Message Encapsulation Format of Nearest Non-TPMR Bridge Agent
By default, LLDP frames are encapsulated in Ethernet format. LLDP-CDP packets use only SNAP encapsulation.
Message Encapsulation Format of Nearest Customer Bridge Agent
By default, LLDP frames are encapsulated in Ethernet format. LLDP-CDP packets use only SNAP encapsulation.
Interface CDP Compatibility
When the device is directly connected to a Cisco device that supports only Cisco Discovery Protocol (CDP) and does not support LLDP, you can configure the CDP-compatible LLDP feature to interact With the directly connected device.
Configuration Change Polling
When the device is directly connected to a Cisco device that supports only Cisco Discovery Protocol (CDP) and does not support LLDP, you can configure the CDP-compatible LLDP feature to interact With the directly connected device.
LLDP Trapping
LLDP trapping notifies the network management system of events such as newly detected neighboring devices and link failures. In the early stage of networking, the network topology changes frequently. If LLDP trapping is enabled, the device will frequently send trap information to the network management system, which increases the system burden and wastes resources. As a best practice, do not enable LLDP trapping or LLDP-MED trapping in the early stage of networking.