Configuring Link Layer Discovery Protocol

This feature module describes how to configure Link Layer Discovery Protocol (LLDP) on the Cisco ASR 901 Aggregation Series Router. The Cisco Discovery Protocol (CDP) is a device discovery protocol that runs over the data-link layer (Layer 2) 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 that are connected to the network.

To permit the discovery of non-Cisco devices, Cisco ASR 901supports LLDP, a vendor-neutral device discovery protocol that is defined in the IEEE 802.1ab standard. LLDP allows network devices to advertise information about themselves to other devices on the network.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information for LLDP.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn . An account on Cisco.com is not required.

Restrictions for LLDP

The following are the restrictions for LLDP:

  • The memory available on a given end network device dictates the number of neighbor entries recorded. However, under most operating conditions, end devices such as printers, IP phones, workstations and so on, are typically operated in the receive mode only.
  • If Entity MIB are used for LLDP broadcast, such as to create a sender ID. LLDP can be configured only when these MIBs are available.

Overview of LLDP

It is an optional element of a protocol stack in the 802 LAN station. LLDP uses the logical link control (LLC) services to transmit and receive information to and from other LLDP agents. LLC provides a Link Service Access Point (LSAP) for access to LLDP. Each LLDP frame is transmitted as a single MAC service request. Each incoming LLDP frame is received at the MAC Service Access Point (MSAP) by the LLC entity as a MAC service indication.

The LLDP protocol operates through the LLDP agent. The tasks of the LLDP agent are to:

  • Collect information from the LLDP local system MIB and transmit it periodically.
  • Receive LLDP frames from neighbors and populate LLDP remote devices MIBs.

LLDP supports a set of attributes used to find the neighbor devices. These attributes are type, length, and value descriptions of devices, and are referred to as Type Length Value (TLV). LLDP supported devices use TLVs to send and receive information from their neighbors. Details such as configuration information, device capabilities, and device identity are also advertised using this protocol.

How to Configure LLDP

This section contains the following procedures:

Configuring LLDP

Complete the following steps to configure LLDP on the Cisco ASR 901 platform:

Procedure

  Command or Action Purpose

Step 1

enable

Example:


Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 3

Do one of the following:

  • lldp run
  • lldp holdtime seconds
  • lldp reinit seconds
  • lldp timer rate
  • lldp lldp tlv-select

Example:


Router(config)# lldp run

Example:


Router(config)# lldp holdtime 100

Example:


Router(config)# lldp reinit 2

Example:


Router(config)# lldp timer 75

Example:


Router(config-if)# lldp tlv-select 
system-description

  • The lldp run command enables LLDP globally on all the interfaces on the router.

  • The lldp holdtime command specifies the hold time. The value ranges from 0 to 65535 seconds. The default value is 120 seconds.

  • The lldp reinit command specifies the delay time in seconds for LLDP to initialize on any interface. The value ranges from 2 to 5 seconds. The default value is 2 seconds.

  • The lldp timer command specifies the rate at which LLDP packets are sent. The value ranges from 5 to 65534 seconds. The default value is 30 seconds.

  • The lldp tlv-select command enables a specific LLDP TLV on a supported interface. Cisco ASR 901 LLDP supports the following TLVs:

    • Port Description—Information about the interface that includes the name of the manufacturer, product name, and the version of the interface.

    • System Description—Textual description of the device.

    • System Name—Assigned name of the device.

    • System Capabilities—Capability of the device and its primary function.

    • Management Address—IP or MAC address of the device.

Step 4

end

Example:


Router(config-if)# end

Returns the CLI to privileged EXEC mode.

Verifying LLDP

To verify LLDP on the Cisco ASR 901 router, use the show command as shown in the following example. 


Router# show lldp ?

entry      Information for specific neighbor entry
errors     LLDP computational errors and overflows
interface  LLDP interface status and configuration
neighbors  LLDP neighbor entries
traffic    LLDP statistics
|          Output modifiers
<cr>



Router# show lldp entry *

Capability codes:
(R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device
(W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other

Configuration Example for LLDP

This section provides the following configuration examples:

Example: Enabling LLDP Globally


Router> enable
Router# configure terminal
Router(config)# lldp run
Router(config)# end

Example: Configuring Hold Time


Router> enable
Router# configure terminal
Router(config)# lldp holdtime 100
Router(config)# end

Example: Configuring Delay Time 


Router> enable
Router# configure terminal
Router(config)# lldp reinit 2
Router(config)# end

Example: Configuring Intervals


Router> enable
Router# configure terminal
Router(config)# lldp timer 75
Router(config)# end

This is an example to enable an LLDP TLV on a supported interface: 


Router> enable
Router# configure terminal
Router(config)# interface ethernet 0/1
Router(config-if)# lldp tlv-select system-description
Router(config-if)# end

Where to go Next

For additional information on configuring Multihop BFD, see the documentation listed in the Additional References section.

Additional References

The following sections provide references related to LLDP feature.

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

Cisco ASR 901 Command Reference

Cisco ASR 901 Series Aggregation Services Router Command Reference

Cisco IOS Interface and Hardware Component Commands

Cisco IOS Interface and Hardware Component Command Reference

Standards

Standard

Title

None

—

MIBs

MIB

MIBs Link

None

To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/c/en/us/td/docs/wireless/asr_901/mib/reference/asr_mib.html

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

—

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for LLDP

LLDP is a one-way protocol that transmits information about the capabilities and current status of a device and its interfaces. LLDP devices use the protocol to solicit information only from other LLDP devices.

Table 1 lists the release history for this feature and provides links to specific configuration information.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn . An account on Cisco.com is not required.


Note
Table 1 lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Table 1. Feature Information for LLDP

Feature Name

Releases

Feature Information

LLDP

12.2(2)SNG

See Overview of LLDP for more information about this feature.