Catalyst 4500 Series Switch Software Configuration Guide, 12.2(50)SG

Configuring LLDP and LLDP-MED

This chapter describes how to configure the Link Layer Discovery Protocol (LLDP) and LLDP Media Endpoint Discovery (LLDP-MED)on the Catalyst 4500 series switch.

Note For complete syntax and usage information for the commands used in this chapter, see the command reference for this release and the "System Management Commands" section in the Cisco IOS Configuration Fundamentals Command Reference, Release 12.2.

This chapter consists of these sections:

•Understanding LLDP and LLDP-MED

•Configuring LLDP and LLDP-MED

•Monitoring and Maintaining LLDP and LLDP-MED

Understanding LLDP and LLDP-MED

This section contains this conceptual information:

•Understanding LLDP

•Understanding LLDP-MED

Understanding LLDP

The Cisco Discovery Protocol (CDP) is a device discovery protocol that runs over Layer 2 (the data link layer) on all Cisco-manufactured devices (routers, bridges, access servers, and switches). CDP allows network management applications to automatically discover and learn about other Cisco devices connected to the network.

To support non-Cisco devices and to allow for interoperability between other devices, the switch supports the IEEE 802.1AB LLDP. LLDP is a neighbor discovery protocol that is used for network devices to advertise information about themselves to other devices on the network. This protocol runs over the data-link layer, which allows two systems running different network layer protocols to learn about each other.

LLDP supports a set of attributes that it uses to discover neighbor devices. These attributes contain type, length, and value descriptions and are referred to as TLVs. LLDP supported devices can use TLVs to receive and send information to their neighbors. Details such as configuration information, device capabilities, and device identity can be advertised using this protocol.

The switch supports the following basic management TLVs, which are optional:

•Port description TLV

•System name TLV

•System description TLV

•System capabilities TLV

• Management address TLV

These organizationally specific LLDP TLVs are also advertised to support LLDP-MED.

•Port VLAN ID TLV ((IEEE 802.1 organizationally specific TLVs)

•MAC/PHY configuration/status TLV(IEEE 802.3 organizationally specific TLVs)

Understanding LLDP-MED

LLDP for Media Endpoint Devices (LLDP-MED) is an extension to LLDP that operates between endpoint devices such as IP phones and network devices such as switches. It specifically provides support for voice over IP (VoIP) applications and provides additional TLVs for capabilities discovery, network policy, Power over Ethernet, inventory management, and location information. By default, all LLDP-MED TLVs are enabled.

LLDP-MED supports these TLVs:

•LLDP-MED capabilities TLV

Allows LLDP-MED endpoints to determine the capabilities that the connected device supports and what capabilities the device has enabled.

•Network policy TLV

Allows both network connectivity devices and endpoints to advertise VLAN configurations and associated Layer 2 and Layer 3 attributes for the specific application on that port. For example, the switch can notify a phone of the VLAN number that it should use. The phone can connect into any switch, obtain its VLAN number, and then start communicating with the call control

•Power management TLV

Enables advanced power management between LLDP-MED endpoint and network connectivity devices. Allows switches and phones to convey power information, such as how the device is powered, power priority, and how much power the device needs.

Note Power Management TLV only exchanges power information; it does not perfornm power negotiation, which is handled by CDP.

•Inventory management TLV

Allows an endpoint to send detailed inventory information about itself to the switch, including information hardware revision, firmware version, software version, serial number, manufacturer name, model name, and asset ID TLV.

•Location TLV

Provides location information from the switch to the endpoint device. The location TLV can send this information:

–Civic location information

Provides the civic address information and postal information. Examples of civic location information are street address, road name, and postal community name information.

–ELIN location information

Provides the location information of a caller. The location is determined by the Emergency location identifier number (ELIN), which is a phone number that routes an emergency call to the local public safety answering point (PSAP) and which the PSAP can use to call back the emergency caller.

Note A switch cannot send LLDP and LLDP-MED simultaneously to an end point device. By default, a network device sends only LLDP packets until it receives LLDP-MED packets from an endpoint device. The network device then sends LLDP-MED packets until it receives only LLDP packets.

Configuring LLDP and LLDP-MED

This section contains this configuration information:

•Default LLDP Configuration

•Configuring LLDP Characteristics

•Disabling and Enabling LLDP Globally

•Disabling and Enabling LLDP on an Interface

•Configuring LLDP-MED TLVs

Default LLDP Configuration

Table 26-1 shows the default LLDP configuration. To change the default settings, use the LLDP global configuration and LLDP interface configuration commands.

Configuring LLDP Characteristics

You can configure the frequency of LLDP updates, the amount of time to hold the information before discarding it, the initialization delay time. You can also select the LLDP and LLDP-MED TLVs for sending and receiving.

To configure these characteristics, perform the follow:

Note Steps 2 through 5 can be performed in any order.

Note Use the no form of each of the LLDP commands to return to the default setting.

This example shows how to configure a holdtime of 120 second, a delay time of 2 seconds and an update frequency of 30:

Switch# configure terminal

Switch(config)# lldp holdtime 120

Switch(config)# lldp reinit 2

Switch(config)# lldp timer 30

Switch(config)# end

This example shows how to transmit only LLDP packets:

switch# configure terminal

siwtch(config)# no lldp receive

switch(config)# end

If you want to receive LLDP packets again, do the following:

switch# configure terminal

siwtch(config)# lldp receive

switch(config)# end

For additional LLDP show commands, see the "Monitoring and Maintaining LLDP and LLDP-MED" section.

Disabling and Enabling LLDP Globally

Note LLDP is disabled by default.

To disable LLDP globally, do the following:

To enable LLDP once it has been disabled, do the following:

This example shows how to globally disable LLDP.

Switch# configure terminal

Switch(config)# no lldp run

Switch(config)# end

This example shows how to globally enable LLDP.

Switch# configure terminal

Switch(config)# lldp run

Switch(config)# end

Disabling and Enabling LLDP on an Interface

LLDP is disabled globally on all supported interfaces. You must enable LLDP globally to allow a device to send LLDP packets. However, no changes are required at the interface level.

You can configure the interface to selectively not to send and receive LLDP packets with the
no lldp transmit and no lldp receive commands.

Note If the interface is configured as a tunnel port, LLDP is automatically disabled.

To disable LLDP on an interface, do the following:

To enable LLDP on an interface once it has been disabled, do the following:

This example shows how to enable LLDP on an interface.

Switch# configure terminal

Switch(config)# interface GigabitEthernet 1/1

Switch(config-if)# lldp transmit

Switch(config-if)# lldp receive

Switch(config-if)# end

Configuring LLDP-MED TLVs

By default, the switch only sends LLDP packets until it receives LLDP-MED packets from the end device. The switch continues to send LLDP-MED packets until it only receives LLDP packets.

By using the lldp interface configuration command, you can configure the interface not to send the TLVs listed in Table 26-2.

To disable a TLV on an interface, do the following:

To enable a TLV on an interface, do the following:

This example shows how to enable a TLV on an interface when it has been disabled.

Switch# configure terminal

Switch(config)# interface GigabitEthernet1/0/1

Switch(config-if)# lldp med-tlv-select inventory management

Switch(config-if)# end

Monitoring and Maintaining LLDP and LLDP-MED

To monitor and maintain LLDP and LLDP-MED on your device, perform one or more of the following tasks, beginning in privileged EXEC mode: