Configuring LLDP· 1

Overview·· 1

Basic concepts 1

Work mechanism·· 6

Protocols and standards 6

LLDP configuration task list 6

Performing basic LLDP configuration· 7

Enabling LLDP· 7

Setting the LLDP operating mode· 7

Setting the LLDP re-initialization delay· 8

Enabling LLDP polling· 8

Configuring the advertisable TLVs 8

Configuring the management address and its encoding format 9

Setting other LLDP parameters 10

Setting an encapsulation format for LLDPDUs 11

Configuring CDP compatibility· 11

Configuration prerequisites 12

Configuring CDP compatibility· 12

Configuring LLDP trapping and LLDP-MED trapping· 12

Displaying and maintaining LLDP· 13

Basic LLDP configuration example· 13

 

Overview

In a heterogeneous network, a standard configuration exchange platform ensures that different types of network devices from different vendors can discover one another and exchange configuration for the sake of interoperability and management.

The IETF drafted the Link Layer Discovery Protocol (LLDP) in IEEE 802.1AB. The protocol operates on the data link layer to exchange device information between directly connected devices. With LLDP, a device sends local device information (including its major functions, management IP address, device ID, and port ID) as TLV (type, length, and value) triplets in LLDP Data Units (LLDPDUs) to the directly connected devices. At the same time, the device stores the device information received in LLDPDUs sent from the LLDP neighbors in a standard MIB. For more information about MIBs, see Network Management and Monitoring Configuration Guide. LLDP enables a network management system to quickly detect and identify Layer 2 network topology changes.

Basic concepts

LLDP agent

An LLDP agent is a mapping of an entity where LLDP runs. Multiple LLDP agents can run on an interface at the same time. LLDP agents are divided into the following types: nearest bridge agent, nearest customer bridge agent, and nearest non-TPMR bridge agent. A Two-port MAC Relay (TPMR) is a type of bridge that has only two externally-accessible bridge ports, and supports a subset of the functions of a MAC bridge. A TPMR is transparent to all frame-based media independent protocols except those destined to it and those destined to reserved MAC addresses that the relay function of the TPMR is defined not to forward. LLDP exchanges packets between neighbor agents and creates and maintains neighbor information for them. Figure 1 shows the neighbor relationships for these LLDP agents. LLDP has two bridge modes: customer bridge (CB) and service bridge (SB).

Figure 1 LLDP neighbor relationships

 

LLDPDU formats   

LLDP sends device information in LLDPDUs. LLDPDUs are encapsulated in Ethernet II or SNAP frames.

1.      LLDPDU encapsulated in Ethernet II

Figure 2 Ethernet II-encapsulated LLDPDU

 

Table 1 Fields in an Ethernet II-encapsulated LLDPDU

Field	Description
Destination MAC address	MAC address to which the LLDPDU is advertised. To distinguish between LLDP packets sent and received by different agent types on the same interface, LLDP specifies different multicast MAC addresses as destination MAC addresses for LLDP packets to different agent types. It is fixed to multicast MAC address 0x0180-C200-000E (only for LLDP packets destined for the nearest bridge neighbor), 0x0180-C200-0000 (only for LLDP packets destined for the nearest customer bridge neighbor), or 0x0180-C200-0003 (only for LLDP packets destined for the nearest non-two-port MAC relay (TPMR) bridge neighbor).
Source MAC address	MAC address of the sending port.
Type	Ethernet type for the upper layer protocol. It is 0x88CC for LLDP.
Data	LLDPDU.
FCS	Frame check sequence, a 32-bit CRC value used to determine the validity of the received Ethernet frame.

 

2.      LLDPDU encapsulated in SNAP

Figure 3 SNAP-encapsulated LLDPDU format

 

Table 2 Fields in a SNAP-encapsulated LLDPDU

Field	Description
Destination MAC address	MAC address to which the LLDPDU is advertised. It is fixed at 0x0180-C200-000E, a multicast MAC address.
Source MAC address	MAC address of the sending port.
Type	SNAP type for the upper layer protocol. It is 0xAAAA-0300-0000-88CC for LLDP.
Data	LLDPDU.
FCS	Frame check sequence, a 32-bit CRC value used to determine the validity of the received Ethernet frame.

 

LLDPDUs

LLDP uses LLDPDUs to exchange information. An LLDPDU comprises multiple TLV sequences. Each TLV carries a type of device information, as shown in Figure 4.

Figure 4 LLDPDU encapsulation format

 

An LLDPDU can carry up to 28 types of TLVs. Mandatory TLVs include Chassis ID TLV, Port ID TLV, Time to Live TLV, and End of LLDPDU TLV. Other TLVs are optional.

TLVs 

TLVs are type, length, and value sequences that carry information elements.

LLDPDU TLVs fall into the following categories:

·           Basic management TLVs

·           Organizationally (IEEE 802.1 and IEEE 802.3) specific TLVs

·           LLDP-MED (media endpoint discovery) TLVs

Basic management TLVs are essential to device management. Organizationally specific TLVs and LLDP-MED TLVs are used for enhanced device management; they are defined by standardization or other organizations and are optional to LLDPDUs.

1.      Basic management TLVs

Table 3 lists the basic management TLV types. Some of them are mandatory to LLDPDUs (they must be included in every LLDPDU).

Table 3 Basic management TLVs

Type	Description	Remarks
Chassis ID	Specifies the bridge MAC address of the sending device.	Mandatory.
Port ID	Specifies the ID of the sending port. If the LLDPDU carries LLDP-MED TLVs, the port ID TLV carries the MAC address of the sending port. Otherwise, the port ID TLV carries the port name.
Time to Live	Specifies the life of the transmitted information on the receiving device.
End of LLDPDU	Marks the end of the TLV sequence in the LLDPDU.
Port Description	Specifies the port description of the sending port.	Optional.
System Name	Specifies the assigned name of the sending device.
System Description	Specifies the description of the sending device.
System Capabilities	Identifies the primary functions of the sending device and the enabled primary functions.
Management Address	Specifies the management address, and the interface number and object identifier (OID) associated with the address.

 

2.      IEEE 802.1 organizationally specific TLVs

Table 4 IEEE 802.1 organizationally specific TLVs

Type	Description
Port VLAN ID	Specifies the port’s VLAN identifier (PVID). An LLDPDU carries only one TLV of this type.
Port And Protocol VLAN ID	Indicates whether the device supports protocol VLANs and, if so, what VLAN IDs these protocols will be associated with. An LLDPDU can carry multiple different TLVs of this type.
VLAN Name	Specifies the textual name of any VLAN to which the port belongs. An LLDPDU can carry multiple different TLVs of this type.
Protocol Identity	Indicates protocols supported on the port. An LLDPDU can carry multiple different TLVs of this type.
DCBX	Data center bridging exchange protocol.

 

NOTE: ·       H3C devices support only receiving protocol identity TLVs. ·       Layer 3 Ethernet ports do not support IEEE 802.1 organizationally specific TLVs.

 

3.      IEEE 802.3 organizationally specific TLVs

Table 5 IEEE 802.3 organizationally specific TLVs

Type	Description
MAC/PHY Configuration/Status	Contains the bit-rate and duplex capabilities of the sending port, support for autonegotiation, enabling status of autonegotiation, and the current rate and duplex mode.
Power Via MDI	Contains the power supply capability of the port, including the PoE type (PSE or PD), PoE mode, whether PSE power supply is supported, whether PSE power supply is enabled, and whether the PoE mode is controllable.
Link Aggregation	Indicates the aggregation capability of the port (whether the link is capable of being aggregated), and the aggregation status (whether the link is in an aggregation).
Maximum Frame Size	Indicates the supported maximum frame size. It is now the MTU of the port.
Power Stateful Control	Indicates the power state control configured on the sending port, including the power type of the PSE/PD, PoE sourcing/receiving priority, and PoE sourcing/receiving power.

 

NOTE: ·       The Power Stateful Control TLV is defined in IEEE P802.3at D1.0 and is not supported in later versions. The device sends this type of TLVs only after receiving them. ·       The switch cannot send MAC/PHY Configuration/Status TLVs but can receive them.

 

LLDP-MED TLVs 

LLDP-MED TLVs provide multiple advanced applications for voice over IP (VoIP), such as basic configuration, network policy configuration, and address and directory management. LLDP-MED TLVs provide a cost-effective and easy-to-use solution for deploying voice devices in Ethernet. LLDP-MED TLVs are shown in Table 6.

Table 6 LLDP-MED TLVs

Type	Description
LLDP-MED Capabilities	Allows a network device to advertise the LLDP-MED TLVs that it supports.
Network Policy	Allows a network device or terminal device to advertise the VLAN ID of the specific port, the VLAN type, and the Layer 2 and Layer 3 priorities for specific applications.
Extended Power-via-MDI	Allows a network device or terminal device to advertise power supply capability. This TLV is an extension of the Power Via MDI TLV.
Hardware Revision	Allows a terminal device to advertise its hardware version.
Firmware Revision	Allows a terminal device to advertise its firmware version.
Software Revision	Allows a terminal device to advertise its software version.
Serial Number	Allows a terminal device to advertise its serial number.
Manufacturer Name	Allows a terminal device to advertise its vendor name.
Model Name	Allows a terminal device to advertise its model name.
Asset ID	Allows a terminal device to advertise its asset ID. The typical case is that the user specifies the asset ID for the endpoint to facilitate directory management and asset tracking.
Location Identification	Allows a network device to advertise the appropriate location identifier information for a terminal device to use in the context of location-based applications.

 

NOTE: If the MAC/PHY configuration/status TLV is not advertisable, none of the LLDP-MED TLVs will be advertised even if they are advertisable. If the LLDP-MED capabilities TLV is not advertisable, the other LLDP-MED TLVs will not be advertised even if they are advertisable.

 

Management address

The network management system uses the management address of a device to identify and manage the device for topology maintenance and network management. The management address is encapsulated in the management address TLV.

Work mechanism

LLDP operating modes        

LLDP can operate in one of the following modes:

·           TxRx mode—A port in this mode can send and receive LLDPDUs.

·           Tx mode—A port in this mode can only send LLDPDUs.

·           Rx mode—A port in this mode can only receive LLDPDUs.

·           Disable mode—A port in this mode cannot send or receive LLDPDUs.

Each time the LLDP operating mode of a port changes, its LLDP protocol state machine re-initializes. A configurable re-initialization delay prevents frequent initializations because of frequent changes to the operating mode. With this delay configured, before a port can initialize LLDP, it must wait for the specified interval after the LLDP operating mode changes.

Transmitting LLDPDUs    

An LLDP-enabled port operating in TxRx mode or Tx mode sends LLDPDUs to its directly connected devices both periodically and when the local configuration changes. To prevent LLDPDUs from overwhelming the network during times of frequent changes to local device information, you can set a delay between two successive LLDPDUs.

This interval is shortened to 1 second in either of the following cases:

·           A new neighbor is discovered. A new LLDPDU is received and carries device information new to the local device.

·           The LLDP operating mode of the port changes from Disable or Rx to TxRx or Tx.

This is the fast sending mechanism of LLDP. With this mechanism, a specific number of LLDPDUs are sent successively at 1-second intervals to help LLDP neighbors discover the local device as soon as possible. Then, the normal LLDPDU transmit interval resumes.

Receiving LLDPDUs   

An LLDP-enabled port that is operating in TxRx mode or Rx mode checks the validity of TLVs carried in every received LLDPDU. If valid, the information is saved and an aging timer is set for it based on the TTL value in the TTL TLV carried in the LLDPDU. If the TTL value is zero, the information ages out immediately.

Protocols and standards  

·           IEEE 802.1AB-2005, Station and Media Access Control Connectivity Discovery

·           ANSI/TIA-1057, Link Layer Discovery Protocol for Media Endpoint Devices

·           DCB Capability Exchange Protocol Specification Rev 1.00

·           DCB Capability Exchange Protocol Base Specification Rev 1.01

LLDP configuration task list  

 

Tasks at a glance
Performing basic LLDP configuration: ·       (Required.) Enabling LLDP ·       (Optional.) Setting the LLDP operating mode ·       (Optional.) Setting the LLDP re-initialization delay ·       (Optional.) Enabling LLDP polling ·       (Optional.) Configuring the advertisable TLVs ·       (Optional.) Configuring the management address and its encoding format ·       (Optional.) Setting other LLDP parameters ·       (Optional.) Setting an encapsulation format for LLDPDUs
(Optional.) Configuring CDP compatibility
(Optional.) Configuring LLDP trapping and LLDP-MED trapping

 

Performing basic LLDP configuration  

Enabling LLDP  

To make LLDP take effect on specific ports, you must enable LLDP both globally and on these ports.

To enable LLDP:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enable LLDP globally.	lldp global enable	By default, LLDP is globally disabled.
3.     Enter Layer 2 or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
4.     (Optional.) Enable LLDP.	lldp enable	By default, LLDP is enabled on a port.

 

Setting the LLDP operating mode          

LLDP can operate in one of the following modes:

·           TxRx mode—A port in this mode can send and receive LLDPDUs.

·           Tx mode—A port in this mode can only send LLDPDUs.

·           Rx mode—A port in this mode can only receive LLDPDUs.

·           Disable mode—A port in this mode cannot send or receive LLDPDUs.

To set the LLDP operating mode:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enter Layer 2 or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3.     Set the LLDP operating mode.	lldp admin-status { disable | rx | tx | txrx }	The default setting is txrx.

 

Setting the LLDP re-initialization delay

When LLDP operating mode changes on a port, the port initializes the protocol state machines after a certain delay. By adjusting the LLDP re-initialization delay, you can avoid frequent initializations caused by frequent changes to the LLDP operating mode on a port.

To set the LLDP re-initialization delay for ports:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Set the LLDP re-initialization delay.	lldp timer reinit-delay delay	The default setting is 2 seconds.

 

Enabling LLDP polling

With LLDP polling enabled, a device periodically searches for local configuration changes. When the device detects a configuration change, it sends LLDPDUs to inform neighboring devices of the change.

To enable LLDP polling:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enter Layer 2 or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3.     Enable LLDP polling and set the polling interval.	lldp check-change-interval interval	By default, LLDP polling is disabled.

 

Configuring the advertisable TLVs

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enter Layer 2 or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3.     Configure the advertisable TLVs (Layer 2 Ethernet interface view).	lldp tlv-enable { basic-tlv { all | management-address-tlv [ ip-address ] | port-description | system-capability | system-description | system-name } | dot1-tlv { all | port-vlan-id | protocol-vlan-id [ vlan-id ] | vlan-name [ vlan-id ] } | dot3-tlv { all | link-aggregation | mac-physic | max-frame-size | power } | med-tlv { all | capability | inventory | location-id { civic-address device-type country-code { ca-type ca-value }&<1-10> | elin-address tel-number } | network-policy | power-over-ethernet } }	By default, all types of LLDP TLVs except the location identification TLV are advertisable on a Layer 2 Ethernet port.
4.     Configure the advertisable TLVs (Layer 3 Ethernet interface view).	lldp tlv-enable { basic-tlv { all | management-address-tlv [ ip-address ] | port-description | system-capability | system-description | system-name } | dot3-tlv { all | link-aggregation | mac-physic | max-frame-size | power } | med-tlv { all | capability | inventory | location-id { civic-address device-type country-code { ca-type ca-value }&<1-10> | elin-address tel-number } | power-over-ethernet } }	By default, all types of LLDP TLVs except the IEEE 802.1 organizationally specific TLVs, network policy TLVs, and location identification TLVs are advertisable on a Layer 3 Ethernet port.

 

Configuring the management address and its encoding format 

LLDP encodes management addresses in numeric or string format in management address TLVs.

By default, management addresses are encoded in numeric format. If a neighbor encodes its management address in character string format, you must configure the encoding format of the management address as string on the connecting port to guarantee normal communication with the neighbor.

To configure a management address to be advertised and its encoding format on a port:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enter Layer 2 or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3.     Allow LLDP to advertise the management address in LLDPDUs and configure the advertised management address.	lldp tlv-enable basic-tlv management-address-tlv [ ip-address ]	By default, the management address is sent through LLDPDUs. ·       For a Layer 2 Ethernet port, the management address is the main IP address of the VLAN interface that is in up state and whose corresponding VLAN ID is the lowest among the VLANs permitted on the port. If none of the VLAN interfaces of the permitted VLANs is assigned an IP address or all VLAN interfaces are down, no management address will be advertised. ·       For a Layer 3 Ethernet port, the management address is its own IP address. If no IP address is configured for the Layer 3 Ethernet port, no management address will be advertised.
4.     Configure the encoding format of the management address as character string.	lldp management-address-format string	By default, the management address is encapsulated in the numeric format.

 

Setting other LLDP parameters  

The TTL 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, which determines how long information about the local device can be saved on a neighboring device. The TTL is expressed by using the following formula:

TTL = Min (65535, (TTL multiplier × LLDPDU transmit interval))

As the expression shows, the TTL can be up to 65535 seconds. TTLs greater than 65535 will be rounded down to 65535 seconds.

Follow these guidelines when you change LLDP parameters:

·           To make sure that LLDP neighbors can receive LLDPDUs to update information about the current device before it ages out, configure the LLDPDU transmit delay to be less than the TTL.

·           Set the LLDPDU transmit interval to be no less than four times the LLDPDU transmit delay.

·           If the LLDPDU transmit delay is greater than the LLDPDU transmit interval, the device uses the LLDPDU transmit delay as the transmit interval.

To change LLDP parameters:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Set the TTL multiplier.	lldp hold-multiplier value	The default setting is 4.
3.     Set the LLDPDU transmit interval.	lldp timer tx-interval interval	The default setting is 30 seconds.
4.     Set the LLDPDU transmit delay.	lldp timer tx-delay delay	The default setting is 2 seconds.
5.     Set the number of LLDPDUs sent each time fast LLDPDU transmission is triggered.	lldp fast-count count	The default setting is 3.

 

Setting an encapsulation format for LLDPDUs  

LLDPDUs can be encapsulated in the following formats: Ethernet II or SNAP frames.

·           With Ethernet II encapsulation configured, an LLDP port sends LLDPDUs in Ethernet II frames.

·           With SNAP encapsulation configured, an LLDP port sends LLDPDUs in SNAP frames.

To set the encapsulation format for LLDPDUs to SNAP:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enter Layer 2 or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3.     Set the encapsulation format for LLDPDUs to SNAP.	lldp encapsulation snap	By default, Ethernet II encapsulation format applies.

 

NOTE: LLDP of earlier versions requires the same encapsulation format on both ends to process LLDPDUs. For this reason, to communicate stably with a neighboring device running LLDP of earlier versions, the local device should be configured with the same encapsulation format.

 

Configuring CDP compatibility

To make your device work with Cisco IP phones, you must enable CDP compatibility.

If your LLDP-enabled device cannot recognize CDP packets, it does not respond to the requests of Cisco IP phones for the voice VLAN ID configured on the device. As a result, a requesting Cisco IP phone sends voice traffic without any tag to your device, and your device cannot differentiate the voice traffic from other types of traffic.

With CDP compatibility enabled, your device can receive and recognize CDP packets from a Cisco IP phone and respond with CDP packets, which carry TLVs with the voice VLAN configuration. According to TLVs with the voice VLAN configuration, the IP phone automatically configures the voice VLAN. As a result, the voice traffic is confined in the configured voice VLAN and is differentiated from other types of traffic.

The switch does not support the voice VLAN function. Therefore, after configured with CDP compatibility, the switch can establish a neighbor relationship with Cisco devices, but it cannot exchange voice VLAN information with them.

Configuration prerequisites

Before you configure CDP compatibility, complete the following tasks:

·           Globally enable LLDP.

·           Enable LLDP on the port connecting to an IP phone, and configure the port to operate in TxRx mode.

Configuring CDP compatibility

CDP-compatible LLDP operates in one of the following modes:

·           TxRx—CDP packets can be transmitted and received.

·           Disable—CDP packets cannot be transmitted or received.

LLDP traps are sent periodically, and the interval is configurable. To make CDP-compatible LLDP take effect on specific ports, first enable CDP-compatible LLDP globally, and then configure CDP-compatible LLDP to operate in TxRx mode.

The maximum TTL value that CDP allows is 255 seconds. To make CDP-compatible LLDP work properly with Cisco IP phones, configure the LLDPDU transmit interval to be no more than 1/3 of the TTL value.

To enable LLDP to be compatible with CDP:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enable CDP compatibility globally.	lldp compliance cdp	By default, CDP compatibility is disabled globally.
3.     Enter Layer 2 or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
4.     Configure CDP-compatible LLDP to operate in TxRx mode.	lldp compliance admin-status cdp txrx	By default, CDP-compatible LLDP operates in Disable mode.

 

Configuring LLDP trapping and LLDP-MED trapping          

LLDP trapping or LLDP-MED trapping notifies the network management system of events such as newly detected neighboring devices and link malfunctions.

To prevent excessive LLDP traps from being sent when the topology is unstable, set a trap transmit interval for LLDP.

To configure LLDP trapping and LLDP-MED trapping:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enter Layer 2 or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3.     Enable LLDP trapping.	lldp notification remote-change enable	By default, LLDP trapping is disabled.
4.     Enable LLDP-MED trapping.	lldp notification med-topology-change enable	By default, LLDP-MED trapping is disabled.
5.     Return to system view.	quit	N/A
6.     (Optional.) Set the LLDP trap transmit interval.	lldp timer notification-interval interval	The default setting is 5 seconds.

 

Displaying and maintaining LLDP 

Execute display commands in any view.

 

Task	Command
Display the global LLDP information or the information contained in the LLDP TLVs to be sent through a port.	display lldp local-information [ global | interface interface-type interface-number ]
Display the information contained in the LLDP TLVs sent from neighboring devices.	display lldp neighbor-information [ interface interface-type interface-number [ verbose ] | list [ system-name system-name ] | verbose ]
Display LLDP statistics.	display lldp statistics [ global | interface interface-type interface-number ]
Display LLDP status of a port.	display lldp status [ interface interface-type interface-number ]
Display types of advertisable optional LLDP TLVs.	display lldp tlv-config [ interface interface-type interface-number ]

 

Basic LLDP configuration example  

By default, Ethernet, VLAN, and aggregate interfaces are down. To configure such an interface, bring the interface up by executing the undo shutdown command.

Network requirements

As shown in Figure 5, the NMS and Switch A are located in the same Ethernet network. An MED device and Switch B are connected to GigabitEthernet 4/0/1 and GigabitEthernet 4/0/2 of Switch A.

Enable LLDP globally on Switch A and Switch B to monitor the link between Switch A and Switch B and the link between Switch A and the MED device on the NMS.

Figure 5 Network diagram

 

Configuration procedure

1.      Configure Switch A:

# Enable LLDP globally.

<SwitchA> system-view

[SwitchA] lldp global enable

# Enable LLDP on GigabitEthernet 4/0/1 and GigabitEthernet 4/0/2. (You can skip this step because LLDP is enabled on ports by default.) Set the LLDP operating mode to Rx.

[SwitchA] interface GigabitEthernet 4/0/1

[SwitchA-GigabitEthernet4/0/1] lldp enable

[SwitchA-GigabitEthernet4/0/1] lldp admin-status rx

[SwitchA-GigabitEthernet4/0/1] quit

[SwitchA] interface GigabitEthernet 4/0/2

[SwitchA-GigabitEthernet4/0/2] lldp enable

[SwitchA-GigabitEthernet4/0/2] lldp admin-status rx

[SwitchA-GigabitEthernet4/0/2] quit

2.      Configure Switch B:

# Enable LLDP globally.

<SwitchB> system-view

[SwitchB] lldp global enable

# Enable LLDP on GigabitEthernet 4/0/1. (You can skip this step because LLDP is enabled on ports by default.) Set the LLDP operating mode to Tx.

[SwitchB] interface GigabitEthernet 4/0/1

[SwitchB-GigabitEthernet4/0/1] lldp enable

[SwitchB-GigabitEthernet4/0/1] lldp admin-status tx

[SwitchB-GigabitEthernet4/0/1] quit

3.      Verify the configuration:

# Display the global LLDP status and port LLDP status on Switch A.

[SwitchA] display lldp status

Global status of LLDP: Enable

The current number of LLDP neighbors: 2

The current number of CDP neighbors: 0

LLDP neighbor information last changed time: 0 days, 0 hours, 4 minutes, 40 seconds

Transmit interval              : 30s

Hold multiplier                : 4

Reinit delay                   : 2s

Transmit delay                 : 2s

Trap interval                  : 5s

Fast start times               : 3

 

LLDP status information of Port 1 [GigabitEthernet4/0/1]:

Port status of LLDP            : Enable

Admin status                   : RX_Only

Trap flag                      : No

MED trap flag                  : No

Polling interval               : 0s

Number of LLDP neighbors       : 1

Number of MED neighbors        : 1

Number of CDP neighbors        : 0

Number of sent optional TLV    : 0

Number of received unknown TLV : 0

 

LLDP status information of Port 2 [GigabitEthernet4/0/2]:

Port status of LLDP            : Enable

Admin status                   : RX_Only

Trap flag                      : No

MED trap flag                  : No

Polling interval               : 0s

Number of LLDP neighbors       : 1

Number of MED neighbors        : 0

Number of CDP neighbors        : 0

Number of sent optional TLV    : 0

Number of received unknown TLV : 3

The sample output shows that:

?  GigabitEthernet 4/0/1 of Switch A connects to an MED device.

?  GigabitEthernet 4/0/2 of Switch A connects to a non-MED device.

?  Both ports operate in Rx mode, and they can receive LLDPDUs but cannot send LLDPDUs.

# Remove the link between Switch A and Switch B, and then display the global LLDP status and port LLDP status on Switch A.

[SwitchA] display lldp status

Global status of LLDP: Enable

The current number of LLDP neighbors: 1

The current number of CDP neighbors: 0

LLDP neighbor information last changed time: 0 days, 0 hours, 5 minutes, 20 seconds

Transmit interval              : 30s

Hold multiplier                : 4

Reinit delay                   : 2s

Transmit delay                 : 2s

Trap interval                  : 5s

Fast start times               : 3

 

LLDP status information of Port 1 [GigabitEthernet4/0/1]:

Port status of LLDP            : Enable

Admin status                   : RX_Only

Trap flag                      : No

MED trap flag                  : No

Polling interval               : 0s

Number of LLDP neighbors       : 1

Number of MED neighbors        : 1

Number of CDP neighbors        : 0

Number of sent optional TLV    : 0

Number of received unknown TLV : 5

 

LLDP status information of Port 2 [GigabitEthernet4/0/2]:

Port status of LLDP            : Enable

Admin status                   : RX_Only

Trap flag                      : No

MED trap flag                  : No

Polling interval               : 0s

Number of LLDP neighbors       : 0

Number of MED neighbors        : 0

Number of CDP neighbors        : 0

Number of sent optional TLV    : 0

Number of received unknown TLV : 0

The sample output shows that GigabitEthernet 4/0/2 of Switch A does not connect to any neighboring devices.