In a heterogeneous network, a standard configuration exchange platform is required for different types of network devices from different vendors to discover one another and exchange configuration information for the sake of interoperability and management.

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 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. LLDP enables a network management system to quickly detect and identify changes to Layer 2 network topology. For more information about MIBs, see Network Management and Monitoring Configuration Guide.

Basic concepts

This section describes the basic concepts of LLDP.

LLDPDU formats

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

1. Ethernet II-encapsulated LLDPDU

Figure 1 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. It is fixed to 0x0180-C200-000E, a multicast MAC address.
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. SNAP-encapsulated LLDPDU

Figure 2 SNAP-encapsulated LLDPDU

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 3.

Figure 3 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. The type field identifies the type of information, the length field measures the length of the information field in octets, and the value field contains the information itself.

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 improved 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, that is, 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 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 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 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.

NOTE:

H3C devices support only receiving protocol identity 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 maximum transmission unit (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. Later versions no longer support this TLV. H3C devices send this type of TLV only after receiving them.

LLDP-MED TLVs

LLDP-MED TLVs provide multiple advanced applications for 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, VLAN type, and 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 assist 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.

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 TLV encapsulates the management address.

Working mechanism

This section describes the working mechanism of LLDP.

LLDP operating modes

LLDP can operate in one of the following modes:

· TxRx mode—A port in this mode sends and receives LLDPDUs.

· Tx mode—A port in this mode only sends LLDPDUs.

· Rx mode—A port in this mode only receives LLDPDUs.

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

Each time the LLDP operating mode of a port changes, its LLDP protocol state machine re-initializes. A re-initialization delay, which is user configurable, prevents LLDP from being initialized too frequently when the operating mode frequently changes. With this delay configured, a port must wait the specified interval after the LLDP operating mode changes before it initializes LLDP.

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 when local device information frequently changes, a port must wait a specified interval 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 new device information 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 quickly discover the local device. 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 Time to Live TLV carried in the LLDPDU. If the TTL value is zero, 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

LLDP configuration task list

Task		Remarks
Performing basic LLDP configuration	Enabling LLDP	Required.
	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.
Enabling LLDP to automatically discover IP phones		Optional
Configuring LLDP trapping		Optional.

NOTE:

LLDP-related configurations made in Ethernet interface view take effect only on the current port, and those made in port group view take effect on all ports in the current port group.

Performing basic LLDP configuration

This section describes how to perform 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
1. Enable LLDP globally.	lldp enable	By default, LLDP is globally enabled.
2. Enter Ethernet interface view or port group view.	· Enter Layer 2 Ethernet interface view: interface interface-type interface-number · Enter port group view: port-group manual port-group-name	Use either command.
3. Enable LLDP.	lldp enable	Optional. 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 sends and receives LLDPDUs.

· Tx mode—A port in this mode only sends LLDPDUs.

· Rx mode—A port in this mode only receives LLDPDUs.

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

To set the LLDP operating mode:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Ethernet interface view or port group view.	· Enter Layer 2 Ethernet interface view: interface interface-type interface-number · Enter port group view: port-group manual port-group-name	Use either command.
3. Set the LLDP operating mode.	lldp admin-status { disable \| rx \| tx \| txrx }	Optional. The default LLDP operating mode 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	Optional. The default setting is 2 seconds.

Step

Command

Remarks

1. Enter system view.

system-view

N/A

2. Set the LLDP re-initialization delay.

lldp timer reinit-delay delay

Optional.

The default setting is 2 seconds.

Enabling LLDP polling

With LLDP polling enabled, a device periodically searches for local configuration changes. On detecting a configuration change, the device 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 Ethernet interface view or port group view.	· Enter Layer 2 Ethernet interface view: interface interface-type interface-number · Enter port group view: port-group manual port-group-name	Use either command.
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 Ethernet interface view or port group view.	· Enter Layer 2 Ethernet interface view: interface interface-type interface-number · Enter port group view: port-group manual port-group-name	Use either command.
3. Configure the advertisable TLVs.	lldp tlv-enable { basic-tlv { all \| 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 } }	Optional. By default, all types of LLDP TLVs except location identification TLVs are advertisable on a Layer 2 Ethernet port.

Configuring the management address and its encoding format

LLDP encodes management addresses in numeric or character 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 or group of ports:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Ethernet interface view or port group view.	· Enter Layer 2 Ethernet interface view: interface interface-type interface-number · Enter port group view: port-group manual port-group-name	Use either command.
3. Allow LLDP to advertise the management address in LLDPDUs and configure the advertised management address.	lldp management-address-tlv [ ip-address ]	Optional. 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 lowest-ID VLAN carried on the port. If none of the carried VLANs is assigned an IP address, no management address will be advertised.
4. Configure the encoding format of the management address as a character string.	lldp management-address-format string	Optional. By default, the management address is encapsulated in numeric format.

Setting other LLDP parameters

The Time to Live TLV carried in an LLDPDU determines how long 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 calculated by using the following formula:

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

As the expression shows, the TTL can be up to 65,535 seconds. TTLs greater than 65,535 will be rounded down to 65,535 seconds.

Configuration restrictions and guidelines

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

· It is a good practice to 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.

Configuration procedure

To change LLDP parameters:

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

Setting an encapsulation format for LLDPDUs

LLDPDUs can be encapsulated in the following formats:

· Ethernet II encapsulation—An LLDP port sends LLDPDUs in Ethernet II frames and processes only incoming Ethernet II encapsulated LLDPDUs.

· SNAP encapsulation—An LLDP port sends LLDPDUs in SNAP frames and processes only incoming SNAP encapsulated LLDPDUs.

By default, Ethernet II frames encapsulate LLDPDUs. If neighbor devices encapsulate LLDPDUs in SNAP frames, configure the encapsulation format for LLDPDUs as SNAP to guarantee normal communication with neighbors.

LLDP-CDP packets use only SNAP encapsulation.

To set the encapsulation format for LLDPDUs to SNAP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Ethernet interface view or port group view.	· Enter Layer 2 Ethernet interface view: interface interface-type interface-number · Enter port group view: port-group manual port-group-name	Use either command.
3. Set the encapsulation format for LLDPDUs to SNAP.	lldp encapsulation snap	By default, Ethernet II encapsulation format applies.

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 requests from Cisco IP phones for the voice VLAN ID configured on the device. When a requesting Cisco IP phone sends voice traffic without any tag to your device, 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 voice VLAN configuration. The IP phone automatically configures the voice VLAN according to the voice VLAN configuration TLVs. As a result, voice traffic is confined in the configured voice VLAN, and differentiated from other types of traffic.

For more information about voice VLANs, see "Configuring voice VLANs."

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

IMPORTANT:

The maximum TTL value that CDP allows is 255 seconds. To make CDP-compatible LLDP work properly with Cisco IP phones, make sure that the product of the TTL multiplier and the LLDPDU transmit interval is less than 255 seconds.

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

· TxRx—CDP packets can be transmitted and received.

· Disable—CDP packets can be neither transmitted nor 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.

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 Ethernet interface view or port group view.	· Enter Layer 2 Ethernet interface view: interface interface-type interface-number · Enter port group view: port-group manual port-group-name	Use either command.
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.

Enabling LLDP to automatically discover IP phones

In a traditional voice VLAN network, the switch maps the source MAC addresses of IP phones to a limited number of OUI addresses to allow them to access the network. This method restricts the types of IP phones on the network, if the IP phones with the source MAC addresses match the same OUI address are categorized as a type.

To break the restriction, you can enable the switch to automatically discover IP phones through LLDP. With this function, the switch can automatically discover the peer, and exchange LLDP TLVs with the peer. If the LLDP System Capabilities TLV received on a port shows that the peer is phone capable, the switch determines that the peer is an IP phone and sends an LLDP TLV carrying the voice VLAN configuration to the peer.

When the IP phone discovery process is complete, the port will automatically join the voice VLAN and improve the transmission priority of the voice traffic for the IP phone. To ensure that the IP phone can pass authentication, the switch will add the MAC address of the IP phone to the MAC address table.

For more information about voice VLANs, see "Configuring voice VLANs."

Configuration prerequisites

Before you enable the switch to automatically discover IP phones through LLDP, complete the following tasks:

· Enable LLDP globally and on ports.

· Configure voice VLANs.

Configuration procedure

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable LLDP to automatically discover IP phones.	voice vlan track lldp	Disabled by default.

IMPORTANT:

· When the switch is enabled to automatically discover IP phones through LLDP, you can connect at most five IP phones to each port of the switch.

· You cannot use this function together with CDP compatibility.

Configuring LLDP trapping

LLDP trapping notifies the NMS 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:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Ethernet interface view or port group view.	· Enter Layer 2 Ethernet interface view: interface interface-type interface-number · Enter port group view: port-group manual port-group-name	Use either command.
3. Enable LLDP trapping.	lldp notification remote-change enable	By default, LLDP trapping is disabled.
4. Return to system view.	quit	N/A
5. Set the LLDP trap transmit interval.	lldp timer notification-interval interval	Optional. The default setting is 5 seconds.

Displaying and maintaining LLDP

Task	Command	Remarks
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 ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view.
Display the information contained in the LLDP TLVs sent from neighboring devices.	display lldp neighbor-information [ brief \| interface interface-type interface-number [ brief ] \| list [ system-name system-name ] ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view.
Display LLDP statistics.	display lldp statistics [ global \| interface interface-type interface-number ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view.
Display LLDP status of a port.	display lldp status [ interface interface-type interface-number ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view.
Display types of advertisable optional LLDP TLVs.	display lldp tlv-config [ interface interface-type interface-number ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view.

LLDP configuration examples

Basic LLDP configuration example

Network requirements

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

Configuration procedure

1. Configure Switch A:

# Enable LLDP globally.

<SwitchA> system-view

[SwitchA] lldp enable

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

[SwitchA] interface gigabitethernet 1/0/1

[SwitchA-GigabitEthernet1/0/1] lldp enable

[SwitchA-GigabitEthernet1/0/1] lldp admin-status rx

[SwitchA-GigabitEthernet1/0/1] quit

[SwitchA] interface gigabitethernet 1/0/2

[SwitchA-GigabitEthernet1/0/2] lldp enable

[SwitchA-GigabitEthernet1/0/2] lldp admin-status rx

[SwitchA-GigabitEthernet1/0/2] quit

2. Configure Switch B:

# Enable LLDP globally.

<SwitchB> system-view

[SwitchB] lldp enable

# Enable LLDP on GigabitEthernet1/0/1. (You can skip this step because LLDP is enabled on ports by default.) Set the LLDP operating mode to Tx.

[SwitchB] interface gigabitethernet 1/0/1

[SwitchB-GigabitEthernet1/0/1] lldp enable

[SwitchB-GigabitEthernet1/0/1] lldp admin-status tx

[SwitchB-GigabitEthernet1/0/1] quit

Verifying 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

Port 1 [GigabitEthernet1/0/1]:

Port status of LLDP : Enable

Admin status : Rx_Only

Trap flag : No

Polling interval : 0s

Number of neighbors: 1

Number of MED neighbors : 1

Number of CDP neighbors : 0

Number of sent optional TLV : 0

Number of received unknown TLV : 0

Port 2 [GigabitEthernet1/0/2]:

Port status of LLDP : Enable

Admin status : Rx_Only

Trap flag : No

Polling interval : 0s

Number of neighbors: 1

Number of MED neighbors : 0

Number of CDP neighbors : 0

Number of sent optional TLV : 0

Number of received unknown TLV : 3

As the sample output shows, GigabitEthernet 1/0/1 of Switch A connects to an MED device, and GigabitEthernet 1/0/2 of Switch A connects to a non-MED device. Both ports operate in Rx mode, and they only receive 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

Port 1 [GigabitEthernet1/0/1]:

Port status of LLDP : Enable

Admin status : Rx_Only

Trap flag : No

Polling interval : 0s

Number of neighbors : 1

Number of MED neighbors : 1

Number of CDP neighbors : 0

Number of sent optional TLV : 0

Number of received unknown TLV : 5

Port 2 [GigabitEthernet1/0/2]:

Port status of LLDP : Enable

Admin status : Rx_Only

Trap flag : No

Polling interval : 0s

Number of neighbors : 0

Number of MED neighbors : 0

Number of CDP neighbors : 0

Number of sent optional TLV : 0

Number of received unknown TLV : 0

As the sample output shows, GigabitEthernet 1/0/2 of Switch A does not connect to any neighboring devices.

CDP-compatible LLDP configuration example

Network requirements

As shown in Figure 5, GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 of Switch A are each connected to a Cisco IP phone. The two IP phones send out tagged voice traffic.

Configure voice VLAN 2 on Switch A. Enable CDP compatibility of LLDP on Switch A to allow the Cisco IP phones to automatically configure the voice VLAN, confining their voice traffic to the voice VLAN to isolate the voice traffic from other types of traffic.

Figure 5 Network diagram

Configuration procedure

1. Configure a voice VLAN on Switch A:

# Create VLAN 2.

<SwitchA> system-view

[SwitchA] vlan 2

[SwitchA-vlan2] quit

# Set the link type of GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 to trunk and enable voice VLAN on them.

[SwitchA] interface gigabitethernet 1/0/1

[SwitchA-GigabitEthernet1/0/1] port link-type trunk

[SwitchA-GigabitEthernet1/0/1] voice vlan 2 enable

[SwitchA-GigabitEthernet1/0/1] quit

[SwitchA] interface gigabitethernet 1/0/2

[SwitchA-GigabitEthernet1/0/2] port link-type trunk

[SwitchA-GigabitEthernet1/0/2] voice vlan 2 enable

[SwitchA-GigabitEthernet1/0/2] quit

2. Configure CDP-compatible LLDP on Switch A:

# Enable LLDP globally and enable LLDP to be compatible with CDP globally.

[SwitchA] lldp enable

[SwitchA] lldp compliance cdp

# Enable LLDP on GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2. (You can skip this step because LLDP is enabled on ports by default.) Configure LLDP to operate in TxRx mode, and configure CDP-compatible LLDP to operate in TxRx mode on GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2.

[SwitchA] interface gigabitethernet 1/0/1

[SwitchA-GigabitEthernet1/0/1] lldp enable

[SwitchA-GigabitEthernet1/0/1] lldp admin-status txrx

[SwitchA-GigabitEthernet1/0/1] lldp compliance admin-status cdp txrx

[SwitchA-GigabitEthernet1/0/1] quit

[SwitchA] interface gigabitethernet 1/0/2

[SwitchA-GigabitEthernet1/0/2] lldp enable

[SwitchA-GigabitEthernet1/0/2] lldp admin-status txrx

[SwitchA-GigabitEthernet1/0/2] lldp compliance admin-status cdp txrx

[SwitchA-GigabitEthernet1/0/2] quit

Verifying the configuration

# Display neighbor information on Switch A.

[SwitchA] display lldp neighbor-information

CDP neighbor-information of port 1[GigabitEthernet1/0/1]:

CDP neighbor index : 1

Chassis ID : SEP00141CBCDBFE

Port ID : Port 1

Software version : P0030301MFG2

Platform : Cisco IP Phone 7960

Duplex : Full

CDP neighbor-information of port 2[GigabitEthernet1/0/2]:

CDP neighbor index : 2

Chassis ID : SEP00141CBCDBFF

Port ID : Port 1

Software version : P0030301MFG2

Platform : Cisco IP Phone 7960

Duplex : Full

As the sample output shows, Switch A has discovered the IP phones connected to GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2, and has obtained their LLDP information.

02-Layer 2-LAN Switching Configuration Guide

LLDPDU formats

LLDPDUs

TLVs

LLDP-MED TLVs

Management address

LLDP operating modes

Transmitting LLDPDUs

Receiving LLDPDUs

Performing basic LLDP configuration

Configuration restrictions and guidelines

Configuration procedure

Configuring LLDP trapping

Verifying the configuration

Verifying the configuration

Intelligent Terminal Products

Product Support Services

Technical Service Solutions

Resource Center

Policy

Online Help

Become a Partner

Partner Policy & Program

Global Learning

Partner Sales Resources

Service Business

News & Events

Contact Us