In a heterogeneous network, a standard configuration exchange platform makes sure different types of network devices from different vendors can discover one another and exchange configuration.

The Link Layer Discovery Protocol (LLDP) is specified 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 as TLV (type, length, and value) triplets in LLDP Data Units (LLDPDUs) to the directly connected devices. Local device information includes its system capabilities, management IP address, device ID, and port ID. The device stores the device information in LLDPDUs 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 the same interface.

LLDP agents are divided into the following types:

· Nearest bridge agent .

· Nearest customer bridge agent.

· 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 for the following:

· Protocols destined to it.

· Protocols destined to reserved MAC addresses that the relay function of the TPMR is configured 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

LLDP frame formats

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

· LLDP frame encapsulated in Ethernet II

Figure 2 Ethernet II-encapsulated LLDP frame

Table 1 Fields in an Ethernet II-encapsulated LLDP frame

Field	Description
Destination MAC address	MAC address to which the LLDP frame is advertised. LLDP specifies different multicast MAC addresses as destination MAC addresses for LLDP frames destined for agents of different types. This helps distinguish between LLDP frames sent and received by different agent types on the same interface. The destination MAC address is fixed to one of the following multicast MAC addresses: · 0x0180-C200-000E for LLDP frames destined for nearest bridge agents. · 0x0180-C200-0000 for LLDP frames destined for nearest customer bridge agents. · 0x0180-C200-0003 for LLDP frames destined for nearest non-TPMR bridge agents.
Source MAC address	MAC address of the sending port.
Type	Ethernet type for the upper-layer protocol. It is 0x88CC for LLDP.
Data	LLDPDU. An LLDP frame contains only one LLDPDU.
FCS	Frame check sequence, a 32-bit CRC value used to determine the validity of the received Ethernet frame.

· LLDP frame encapsulated in SNAP

Figure 3 SNAP-encapsulated LLDP frame

Table 2 Fields in a SNAP-encapsulated LLDP frame

Field	Description
Destination MAC address	MAC address to which the LLDP frame is advertised. It is the same as that for Ethernet II-encapsulated LLDP frames.
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. An LLDP frame contains only one 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 TLVs. Each TLV carries a type of device information, as shown in Figure 4.

Figure 4 LLDPDU encapsulation format

An LLDPDU can carry up to 32 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

A TLV is an information element that contains the type, length, and value fields.

LLDPDU TLVs include 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 for LLDPDUs.

· Basic management TLVs

Table 3 lists the basic management TLV types. Some of them are mandatory for LLDPDUs.

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 description for the sending port.	Optional.
System Name	Specifies the assigned name of the sending device.
System Description	Specifies the description for the sending device.
System Capabilities	Identifies the primary functions of the sending device and the enabled primary functions.
Management Address	Specifies the following elements: · The management address of the local device. · The interface number and object identifier (OID) associated with the address.

· IEEE 802.1 organizationally specific TLVs

Table 4 IEEE 802.1 organizationally specific TLVs

Type	Description
Port VLAN ID	Specifies the port VLAN identifier (PVID).
Port And Protocol VLAN ID	Indicates whether the device supports protocol VLANs and, if so, what VLAN IDs these protocols will be associated with.
VLAN Name	Specifies the textual name of any VLAN to which the port belongs.
Protocol Identity	Indicates protocols supported on the port.
DCBX	Data center bridging exchange protocol. NOTE: The switch does not support DCBX TLV.
EVB module	Edge Virtual Bridging module, including EVB TLV and CDCP TLV. NOTE: The switch does not support EVB TLV.
Link Aggregation	Indicates whether the port supports link aggregation, and if yes, whether link aggregation is enabled.
Management VID	Management VLAN ID.
VID Usage Digest	VLAN ID usage digest.
ETS Configuration	Enhanced Transmission Selection configuration.
ETS Recommendation	ETS recommendation.
PFC	Priority-based Flow Control.
APP	Application protocol.
QCN	Quantized Congestion Notification.

NOTE:

· H3C devices support only receiving protocol identity TLVs and VID usage digest TLVs.

· Layer 3 Ethernet ports support only link aggregation TLVs.

· 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 capabilities of the port: · Port class (PSE or PD). · Power supply mode. · Whether PSE power supply is supported. · Whether PSE power supply is enabled. · Whether pair selection can be controlled. · Power supply type. · Power source. · Power priority. · PD requested power. · PSE allocated power.
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 following: · Power supply mode of the PSE/PD. · PSE/PD priority. · PSE/PD power.

NOTE:

The Power Stateful Control TLV is defined in IEEE P802.3at D1.0 and is not supported in later versions. H3C devices send this type of TLVs only after receiving 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 a 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.

Working mechanism

LLDP operating modes

An LLDP agent can operate in one of the following modes:

· TxRx mode—An LLDP agent in this mode can send and receive LLDP frames.

· Tx mode—An LLDP agent in this mode can only send LLDP frames.

· Rx mode—An LLDP agent in this mode can only receive LLDP frames.

· Disable mode—An LLDP agent in this mode cannot send or receive LLDP frames.

Each time the LLDP operating mode of an LLDP agent changes, its LLDP protocol state machine reinitializes. A configurable reinitialization delay prevents frequent initializations caused by frequent changes to the operating mode. If you configure the reinitialization delay, an LLDP agent must wait the specified amount of time to initialize LLDP after the LLDP operating mode changes.

Transmitting LLDP frames

An LLDP agent operating in TxRx mode or Tx mode sends LLDP frames to its directly connected devices both periodically and when the local configuration changes. To prevent LLDP frames from overwhelming the network during times of frequent changes to local device information, LLDP uses the token bucket mechanism to rate limit LLDP frames. For more information about the token bucket mechanism, see ACL and QoS Configuration Guide.

LLDP automatically enables the fast LLDP frame transmission mechanism in either of the following cases:

· A new neighbor is discovered. 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.

With this mechanism, the specified number of LLDP frames are sent successively at a configurable fast transmission interval to help LLDP neighbors discover the local device as soon as possible. Then, the normal LLDP frame transmission interval resumes.

Receiving LLDP frames

An LLDP agent operating in TxRx mode or Rx mode confirms the validity of TLVs carried in every received LLDP frame. If the TLVs are valid, the LLDP agent saves the information and starts an aging timer. When the TTL value in the Time To Live TLV carried in the LLDP frame becomes zero, the information ages out immediately.

Protocols and standards

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

· IEEE 802.1AB-2009, 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

· IEEE Std 802.1Qaz-2011, Media Access Control (MAC) Bridges and Virtual Bridged Local Area Networks-Amendment 18: Enhanced Transmission Selection for Bandwidth Sharing Between Traffic Classes

LLDP configuration task list

Tasks at a glance
Performing basic LLDP configurations: · (Required.) Enabling LLDP · (Optional.) Configuring the LLDP bridge mode · (Optional.) Setting the LLDP operating mode · (Optional.) Setting the LLDP reinitialization 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 LLDP frames
(Optional.) Configuring CDP compatibility
(Optional.) Configuring LLDP trapping and LLDP-MED trapping

Performing basic LLDP configurations

Enabling LLDP

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

To use LLDP together with OpenFlow, you must enable LLDP globally on OpenFlow switches. As a best practice to prevent LLDP from affecting topology discovery of OpenFlow controllers, disable LLDP on ports of OpenFlow instances. For more information about OpenFlow, see OpenFlow Configuration Guide.

To enable LLDP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable LLDP globally.	lldp global enable	By default: · If the switch starts up with empty configuration, LLDP is disabled globally (initial setting). · If the switch starts up with the default configuration file, LLDP is enabled globally (factory default). For more information about empty configuration and the default configuration file, see Fundamentals Configuration Guide.
3. Enter Layer 2 /Layer 3 Ethernet interface view, management Ethernet interface view, or Layer 2/Layer 3 aggregate interface view.	interface interface-type interface-number	N/A
4. Enable LLDP.	lldp enable	By default, LLDP is enabled on a port.

Configuring the LLDP bridge mode

The following LLDP bridge modes are available:

· Customer bridge mode—In customer bridge mode, LLDP supports nearest bridge agents, nearest non-TPMR bridge agents, and nearest customer bridge agents. LLDP processes the LLDP frames with destination MAC addresses for these agents and transparently transmits the LLDP frames with other destination MAC addresses in VLANs.

· Service bridge mode—In service bridge mode, LLDP supports nearest bridge agents and nearest non-TPMR bridge agents. LLDP processes the LLDP frames with destination MAC addresses for these agents and transparently transmits the LLDP frames with other destination MAC addresses in VLANs.

To configure the LLDP bridge mode:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Configure LLDP to operate in service bridge mode.	lldp mode service-bridge	By default, LLDP operates in customer bridge mode.

Setting the LLDP operating mode

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2/Layer 3 Ethernet interface view, management Ethernet interface view, or Layer 2/Layer 3 aggregate interface view.	interface interface-type interface-number	N/A
3. Set the LLDP operating mode.	· In Layer 2/Layer 3 Ethernet interface view or management Ethernet interface view: lldp [ agent { nearest-customer \| nearest-nontpmr } ] admin-status { disable \| rx \| tx \| txrx } · In Layer 2/Layer 3 aggregate interface view: lldp agent { nearest-customer \| nearest-nontpmr } admin-status { disable \| rx \| tx \| txrx }	By default: · The nearest bridge agent operates in txrx mode. · The nearest customer bridge agent and nearest non-TPMR bridge agent operate in disable mode. In Ethernet interface view, if no agent type is specified, the command configures the operating mode for nearest bridge agents. In aggregate interface view, you can configure the operating mode only for nearest customer bridge agents and nearest non-TPMR bridge agents.

Setting the LLDP reinitialization delay

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

To set the LLDP reinitialization delay for ports:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Set the LLDP reinitialization 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 LLDP frames 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/Layer 3 Ethernet interface view, management Ethernet interface view, or Layer 2/Layer 3 aggregate interface view.	interface interface-type interface-number	N/A
3. Enable LLDP polling and set the polling interval.	· In Layer 2/Layer 3 Ethernet interface view or management Ethernet interface view: lldp [ agent { nearest-customer \| nearest-nontpmr } ] check-change-interval interval · In Layer 2/Layer 3 aggregate interface view: lldp agent { nearest-customer \| nearest-nontpmr } 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/Layer 3 Ethernet interface view, management Ethernet interface view, or Layer 2/Layer 3 aggregate interface view.	interface interface-type interface-number	N/A
3. Configure the advertisable TLVs (in Layer 2 Ethernet interface view).	· lldp tlv-enable { basic-tlv { all \| port-description \| system-capability \| system-description \| system-name \| management-address-tlv [ ip-address ] } \| dot1-tlv { all \| congestion-notification \| port-vlan-id \| link-aggregation \| protocol-vlan-id [ vlan-id ] \| vlan-name [ vlan-id ] \| management-vid [ mvlan-id ] } \| dot3-tlv { all \| mac-physic \| max-frame-size \| power } \| med-tlv { all \| capability \| inventory \| network-policy [ vlan-id ] \|\| power-over-ethernet \| location-id { civic-address device-type country-code { ca-type ca-value }&<1-10> \| elin-address tel-number } } } · lldp agent nearest-nontpmr tlv-enable { basic-tlv { all \| port-description \| system-capability \| system-description \| system-name \| management-address-tlv [ ip-address ] } \| dot1-tlv { all \| congestion-notification \| port-vlan-id \| link-aggregation } } · lldp agent nearest-customer tlv-enable { basic-tlv { all \| port-description \| system-capability \| system-description \| system-name \| management-address-tlv [ ip-address ] } \| dot1-tlv { all \| congestion-notification \| port-vlan-id \| link-aggregation } }	By default: · Nearest bridge agents can advertise all types of LLDP TLVs except the DCBX TLV, location identification TLV, port and protocol VLAN ID TLVs, VLAN name TLVs, and management VLAN ID TLVs. · Nearest non-TPMR bridge agents advertise no TLVs. · Nearest customer bridge agents can advertise basic TLVs and IEEE 802.1 organizationally specific TLVs.
4. Configure the advertisable TLVs (in Layer 3 Ethernet interface view or management Ethernet interface view).	· lldp tlv-enable { basic-tlv { all \| port-description \| system-capability \| system-description \| system-name \| management-address-tlv [ ip-address ] } \| dot1-tlv { all \| link-aggregation } \| dot3-tlv { all \| mac-physic \| max-frame-size \| power } \| med-tlv { all \| capability \| inventory \| power-over-ethernet \| location-id { civic-address device-type country-code { ca-type ca-value }&<1-10> \| elin-address tel-number } } } · lldp agent { nearest-nontpmr \| nearest-customer } tlv-enable { basic-tlv { all \| port-description \| system-capability \| system-description \| system-name \| management-address-tlv [ ip-address ] } \| dot1-tlv { all \| link-aggregation } }	By default: · Nearest bridge agents can advertise all types of LLDP TLVs (only link aggregation TLV in 802.1 organizationally specific TLVs) except network policy TLVs. · Nearest non-TPMR bridge agents advertise no TLVs. · Nearest customer bridge agents can advertise basic TLVs and IEEE 802.1 organizationally specific TLVs (only link aggregation TLV).
5. Configure the advertisable TLVs (in Layer 2 aggregate interface view).	· lldp agent nearest-nontpmr tlv-enable { basic-tlv { all \| management-address-tlv [ ip-address ] \| port-description \| system-capability \| system-description \| system-name } \| dot1-tlv { all \| port-vlan-id } } · lldp agent nearest-customer tlv-enable { basic-tlv { all \| management-address-tlv [ ip-address ] \| port-description \| system-capability \| system-description \| system-name } \| dot1-tlv { all \| port-vlan-id } } · lldp tlv-enable dot1-tlv { protocol-vlan-id [ vlan-id ] \| vlan-name [ vlan-id ] \| management-vid [ mvlan-id ] }	By default: · Nearest non-TPMR bridge agents advertise no TLVs. · Nearest customer bridge agents can advertise basic TLVs and IEEE 802.1 organizationally specific TLVs (only port and protocol VLAN ID TLV, VLAN name TLV, and management VLAN ID TLV). Nearest bridge agents are not supported on Layer 2 aggregate interfaces.
6. Configure the advertisable TLVs (in Layer 3 aggregate interface view).	lldp agent { nearest-nontpmr \| nearest-customer } tlv-enable basic-tlv { all \| management-address-tlv [ ip-address ] \| port-description \| system-capability \| system-description \| system-name }	By default: · Nearest non-TPMR bridge agents advertise no TLVs. · Nearest customer bridge agents can advertise only basic TLVs. Nearest bridge agents are not supported on Layer 3 aggregate interfaces.

A PoE-capable device of the series can act as a PSE. It supports autonegotiating the supplied power with the PD through LLDP. To use the function, you must perform the following tasks:

· Enable PoE and LLDP on the device.

· Enable PoE and LLDP on the port of the device connected to the PD.

· Configure the power field in IEEE 802.3 organizationally specific TLVs to enable the port to send power via MDI TLVs.

For more information about PoE, see Network Management and Monitoring Configuration Guide.

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 string format, configure the encoding format of the management address as string on the connecting port. This guarantees 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/Layer 3 Ethernet interface view, management Ethernet interface view, or Layer 2/Layer 3 aggregate interface view.	interface interface-type interface-number	N/A
3. Allow LLDP to advertise the management address in LLDP frames and configure the advertised management address.	· In Layer 2/Layer 3 Ethernet interface view or management Ethernet interface view: lldp [ agent { nearest-customer \| nearest-nontpmr } ] tlv-enable basic-tlv management-address-tlv [ ip-address ] · In Layer 2/Layer 3 aggregate interface view: lldp agent { nearest-customer \| nearest-nontpmr } tlv-enable basic-tlv management-address-tlv [ ip-address ]	By default: · Nearest bridge agents and nearest customer bridge agents can advertise the management address in LLDP frames. · Nearest non-TPMR bridge agents cannot advertise the management address in LLDP frames.
4. Configure the encoding format of the management address as string.	· In Layer 2/Layer 3 Ethernet interface view or management Ethernet interface view: lldp [ agent { nearest-customer \| nearest-nontpmr } ] management-address-format string · In Layer 2/Layer 3 aggregate interface view: lldp agent { nearest-customer \| nearest-nontpmr } management-address-format string	By default, the encoding format of the management address is numeric.

Setting other LLDP parameters

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, 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 × 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.

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 LLDP frame transmission interval.	lldp timer tx-interval interval	The default setting is 30 seconds.
4. Set the token bucket size for sending LLDP frames.	lldp max-credit credit-value	The default setting is 5.
5. Set the number of LLDP frames sent each time fast LLDP frame transmission is triggered.	lldp fast-count count	The default setting is 4.
6. Set the interval for fast LLDP frame transmission.	lldp timer fast-interval interval	The default setting is 1 second.

Setting an encapsulation format for LLDP frames

LLDP frames can be encapsulated in the following formats:

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

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

LLDP of earlier versions requires the same encapsulation format on both ends to process LLDP frames. To successfully communicate with a neighboring device running LLDP of earlier versions, the local device must be configured with the same encapsulation format.

To set the encapsulation format for LLDP frames to SNAP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2/Layer 3 Ethernet interface view, management Ethernet interface view, or Layer 2/Layer 3 aggregate interface view.	interface interface-type interface-number	N/A
3. Set the encapsulation format for LLDP frames to SNAP.	· In Layer 2/Layer 3 Ethernet interface view or management Ethernet interface view: lldp [ agent { nearest-customer \| nearest-nontpmr } ] encapsulation snap · In Layer 2/Layer 3 aggregate interface view: lldp agent { nearest-customer \| nearest-nontpmr } encapsulation snap	By default, Ethernet II encapsulation format applies.

Configuring CDP compatibility

When the switch is directly connected to a Cisco device that supports only CDP rather than LLDP, you can enable CDP compatibility to enable the switch to exchange information with the directly-connected device.

CDP compatibility enables the switch to use LLDP to receive and recognize CDP packets from the directly-connected device and send CDP packets to the directly-connected device. The packets that the switch sends to the neighboring CDP device carry the following information:

· Device ID.

· ID of the port connecting to the neighboring device.

· port IP address.

· PVID.

· TTL.

The port IP address is the primary IP address of the VLAN interface in up state. The VLAN ID of the VLAN interface must be the lowest among the VLANs permitted on the port. If no VLAN interfaces of the permitted VLANs is assigned an IP address or all VLAN interfaces are down, no port IP address will be advertised.

The CDP neighbor-information-related fields in the output of the display lldp neighbor-information command show the CDP neighboring device information that can be recognized by the switch. For more information about the display lldp neighbor-information command, see Layer 2—LAN Switching Command Reference.

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 VLAN tag to your device. Your device cannot differentiate the voice traffic from other types of traffic.

CDP compatibility enables your device to receive and recognize CDP packets from a Cisco IP phone and respond with CDP packets carrying 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.

When the device is connected to a Cisco IP phone that has a host attached to its data port, the host must access the network through the Cisco IP phone. If the data port goes down, the IP phone will send a CDP packet to the device so the device can log out the user.

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 a device supporting CDP.

· Configure LLDP to operate in TxRx mode on the port.

Configuration procedure

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.

To make CDP-compatible LLDP take effect on ports, follow these steps:

1. Enable CDP-compatible LLDP globally.

2. 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 correctly with Cisco IP phones, configure the LLDP frame transmission 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/Layer 3 Ethernet interface view or management 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 failures.

To prevent excessive LLDP traps from being sent when the topology is unstable, set a trap transmission 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/Layer 3 Ethernet interface view, management Ethernet interface view, or Layer 2/Layer 3 aggregate interface view.	interface interface-type interface-number	N/A
3. Enable LLDP trapping.	· In Layer 2/Layer 3 Ethernet interface view or management Ethernet interface view: lldp [ agent { nearest-customer \| nearest-nontpmr } ] notification remote-change enable · In Layer 2/Layer 3 aggregate interface view: lldp agent { nearest-customer \| nearest-nontpmr } notification remote-change enable	By default, LLDP trapping is disabled.
4. Enable LLDP-MED trapping (in Layer 2/Layer 3 Ethernet interface view or management Ethernet interface view).	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 transmission interval.	lldp timer notification-interval interval	The default setting is 30 seconds.

Displaying and maintaining LLDP

Execute display commands in any view.

Task	Command
Display local LLDP information.	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 ] [ agent { nearest-bridge \| nearest-customer \| nearest-nontpmr } ] [ verbose ] ] \| list [ system-name system-name ] ]
Display LLDP statistics.	display lldp statistics [ global \| [ interface interface-type interface-number ] [ agent { nearest-bridge \| nearest-customer \| nearest-nontpmr } ] ]
Display LLDP status of a port.	display lldp status [ interface interface-type interface-number ] [ agent { nearest-bridge \| nearest-customer \| nearest-nontpmr } ]
Display types of advertisable optional LLDP TLVs.	display lldp tlv-config [ interface interface-type interface-number ] [ agent { nearest-bridge \| nearest-customer \| nearest-nontpmr } ]

LLDP configuration examples

Basic LLDP configuration example

Network requirements

As shown in Figure 5, the NMS and Switch A are located in the same Ethernet network. A 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 perform the following tasks:

· Monitor the link between Switch A and Switch B.

· Monitor 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 1/0/1. By default, LLDP is enabled on ports.

[SwitchA] interface gigabitethernet 1/0/1

[SwitchA-GigabitEthernet1/0/1] lldp enable

# Set the LLDP operating mode to Rx.

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

[SwitchA-GigabitEthernet1/0/1] quit

# Enable LLDP on GigabitEthernet 1/0/2. By default, LLDP is enabled on ports.

[SwitchA] interface gigabitethernet 1/0/2

[SwitchA-GigabitEthernet1/0/2] lldp enable

# Set the LLDP operating mode to Rx.

[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 global enable

# Enable LLDP on GigabitEthernet 1/0/1. By default, LLDP is enabled on ports.

[SwitchB] interface gigabitethernet 1/0/1

[SwitchB-GigabitEthernet1/0/1] lldp enable

# Set the LLDP operating mode to Tx.

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

[SwitchB-GigabitEthernet1/0/1] quit

Verify the configuration:

# Verify that:

· GigabitEthernet 1/0/1 of Switch A connects to a MED device.

· GigabitEthernet 1/0/2 of Switch A connects to a non-MED device.

· Both ports operate in Rx mode, and they can receive LLDP frames but cannot send LLDP frames.

[SwitchA] display lldp status

Global status of LLDP: Enable

Bridge mode of LLDP: customer-bridge

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

Fast transmit interval : 1s

Transmit credit max : 5

Hold multiplier : 4

Reinit delay : 2s

Trap interval : 30s

Fast start times : 4

LLDP status information of port 1 [GigabitEthernet1/0/1]:

LLDP agent nearest-bridge:

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 : 21

Number of received unknown TLV : 0

LLDP agent nearest-customer:

Port status of LLDP : Enable

Admin status : Disable

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 : 16

Number of received unknown TLV : 0

LLDP status information of port 2 [GigabitEthernet1/0/2]:

LLDP agent nearest-bridge:

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 : 21

Number of received unknown TLV : 3

LLDP agent nearest-nontpmr:

Port status of LLDP : Enable

Admin status : Disable

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 : 1

Number of received unknown TLV : 0

LLDP agent nearest-customer:

Port status of LLDP : Enable

Admin status : Disable

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 : 16

Number of received unknown TLV : 0

# Remove the link between Switch A and Switch B.

# Verify that GigabitEthernet 1/0/2 of Switch A does not connect to any neighboring devices.

[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

Fast transmit interval : 1s

Transmit credit max : 5

Hold multiplier : 4

Reinit delay : 2s

Trap interval : 30s

Fast start times : 4

LLDP status information of port 1 [GigabitEthernet1/0/1]:

LLDP agent nearest-bridge:

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 agent nearest-nontpmr:

Port status of LLDP : Enable

Admin status : Disable

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 : 1

Number of received unknown TLV : 0

LLDP status information of port 2 [GigabitEthernet1/0/2]:

LLDP agent nearest-bridge:

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

LLDP agent nearest-nontpmr:

Port status of LLDP : Enable

Admin status : Disable

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 : 1

Number of received unknown TLV : 0

LLDP agent nearest-customer:

Port status of LLDP : Enable

Admin status : Disable

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 : 16

Number of received unknown TLV : 0

CDP-compatible LLDP configuration example

Network requirements

As shown in Figure 6, GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 of Switch A are each connected to a Cisco IP phone, which sends VLAN-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. The voice VLAN feature performs the following actions:

· Confines the voice traffic to the voice VLAN.

· Isolates the voice traffic from other types of traffic.

Figure 6 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 CDP compatibility globally.

[SwitchA] lldp global enable

[SwitchA] lldp compliance cdp

# Enable LLDP on GigabitEthernet 1/0/1. By default, LLDP is enabled on ports.

[SwitchA] interface gigabitethernet 1/0/1

[SwitchA-GigabitEthernet1/0/1] lldp enable

# Configure LLDP to operate in TxRx mode on GigabitEthernet 1/0/1.

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

# Configure CDP-compatible LLDP to operate in TxRx mode on GigabitEthernet 1/0/1.

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

[SwitchA-GigabitEthernet1/0/1] quit

# Enable LLDP on GigabitEthernet 1/0/2. By default, LLDP is enabled on ports.

[SwitchA] interface gigabitethernet 1/0/2

[SwitchA-GigabitEthernet1/0/2] lldp enable

# Configure LLDP to operate in TxRx mode on GigabitEthernet 1/0/2.

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

# Configure CDP-compatible LLDP to operate in TxRx mode on GigabitEthernet 1/0/2.

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

[SwitchA-GigabitEthernet1/0/2] quit

Verifying the configuration

# Verify that Switch A has completed the following tasks:

· Discovering the IP phones connected to GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2.

· Obtaining IP phone information.

[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

03-Layer 2-LAN Switching Configuration Guide

LLDP agent

LLDP frame formats

LLDPDUs

TLVs

Management address

LLDP operating modes

Transmitting LLDP frames

Receiving LLDP frames

Performing basic LLDP configurations

Configuring LLDP trapping and LLDP-MED trapping

Network requirements

Configuration procedure

Verify the configuration:

Network requirements

Configuration procedure

Verifying the configuration

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