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Link Layer Discovery Protocol (LLDP)

Mohammed al Baqari
Level 11
Level 11

‎07-08-2015 01:38 PM - edited ‎03-12-2019 10:17 AM

LLDP

 

Link Layer Discovery Protocol (LLDP), standardized by the IEEE as part of 802.1ab, enables standardized discovery of nodes in a multivendor environment.

 

Restrictions:

 

  • Use of LLDP is limited to 802.1 media types such as Ethernet, Token Ring, and Fiber Distributed Data Interface (FDDI) networks. It can't be used for HDLC, Frame-Relay, ATM, etc.
  • LLDP and CDP can run on the same interface

 

LLDP is unidirectional, operating only in an advertising mode. LLDP enabled nodes will send multicast frames out of all LLDP enabled interfaces. LLDP enabled nodes which receive LLDP frames can record information about their neighbors and build their own topology database. Each node can be configured to enable/disable send and/or receive of LLDP frames as separate task.

 

LLDP exchange attributes in the format of TLVs between devices to discover each other.

 

The switch supports these basic management TLVs. These are mandatory LLDP TLVs.

  • 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 
  • MAC/PHY configuration/status TLV

 

LLDP-MED

 

MED is an extension for LLDP that support additional TLVs. LLDP-MED supports the following three classes of endpoints:

 

  • Generic (class 1): Basic participant endpoints; for example, IP communications controllers.
  • Media (class 2): Endpoints that support media streams; for example, media gateways and conference bridges.
  • Communication Device (class 3): Endpoints that support IP communications end users; for example, IP phones and Softphone.

 

By default, a network connectivity device (e.g. switch) sends out only LLDP packets until it receives LLDP-MED packets from an endpoint device (e.g. IP Phone). The network device then sends out LLDP-MED packets until the remote device to which it is connected ceases to be LLDP-MED capable.

 

The additional TLVs supported can be groups as (by default all MED TLVs are enabled):

 

  • Capabilities TLV — Endpoints determine the types of capabilities that a connected device supports and which ones are enabled.

 

MED Information:

 

    MED Codes:

          (NP) Network Policy, (LI) Location Identification

          (PS) Power Source Entity, (PD) Power Device

          (IN) Inventory

 

    H/W revision: 14

    F/W revision: tnp45.9-3-1-CR17.bin

    S/W revision: SCCP45.9-4-2-1S

    Serial number: FCH1714A7PV

    Manufacturer: Cisco Systems, Inc.

    Model: CP-7945G

    Capabilities: NP, PD, IN

    Device type: Endpoint Class III

    Network Policy(Voice): VLAN 104, tagged, Layer-2 priority: 5, DSCP: 46

    Network Policy(Voice Signal): VLAN 104, tagged, Layer-2 priority: 4, DSCP: 32

    PD device, Power source: Unknown, Power Priority: Low, Wattage: 12.0

    Location - not advertised

 

  • Inventory TLV — LLDP-MED support exchange of hardware, software, and firmware versions, among other inventory details.

 

MED Information:

 

    MED Codes:

          (NP) Network Policy, (LI) Location Identification

          (PS) Power Source Entity, (PD) Power Device

          (IN) Inventory

 

    H/W revision: 14

    F/W revision: tnp45.9-3-1-CR17.bin

    S/W revision: SCCP45.9-4-2-1S

    Serial number: FCH1714A7PV

    Manufacturer: Cisco Systems, Inc.

    Model: CP-7945G

    Capabilities: NP, PD, IN

    Device type: Endpoint Class III

    Network Policy(Voice): VLAN 104, tagged, Layer-2 priority: 5, DSCP: 46

    Network Policy(Voice Signal): VLAN 104, tagged, Layer-2 priority: 4, DSCP: 32

    PD device, Power source: Unknown, Power Priority: Low, Wattage: 12.0

    Location - not advertised

 

  • LAN speed and duplex TLV — Devices discover mismatches in speed and duplex settings.
  • Location identification TLV — An endpoint, particularly a telephone, learns its location from a network device. This location information may be used for location-based applications on the telephone and is important when emergency calls are placed.

 

MED Information:

 

    MED Codes:

          (NP) Network Policy, (LI) Location Identification

          (PS) Power Source Entity, (PD) Power Device

          (IN) Inventory

 

    H/W revision: 14

    F/W revision: tnp45.9-3-1-CR17.bin

    S/W revision: SCCP45.9-4-2-1S

    Serial number: FCH1714A7PV

    Manufacturer: Cisco Systems, Inc.

    Model: CP-7945G

    Capabilities: NP, PD, IN

    Device type: Endpoint Class III

    Network Policy(Voice): VLAN 104, tagged, Layer-2 priority: 5, DSCP: 46

    Network Policy(Voice Signal): VLAN 104, tagged, Layer-2 priority: 4, DSCP: 32

    PD device, Power source: Unknown, Power Priority: Low, Wattage: 12.0

    Location - not advertised

 

  • Network policy TLV — Network connectivity devices notify telephones about the VLANs they should use, CoS, and DSCP settings.

 

MED Information:

 

    MED Codes:

          (NP) Network Policy, (LI) Location Identification

          (PS) Power Source Entity, (PD) Power Device

          (IN) Inventory

 

    H/W revision: 14

    F/W revision: tnp45.9-3-1-CR17.bin

    S/W revision: SCCP45.9-4-2-1S

    Serial number: FCH1714A7PV

    Manufacturer: Cisco Systems, Inc.

    Model: CP-7945G

    Capabilities: NP, PD, IN

    Device type: Endpoint Class III

    Network Policy(Voice): VLAN 104, tagged, Layer-2 priority: 5, DSCP: 46

    Network Policy(Voice Signal): VLAN 104, tagged, Layer-2 priority: 4, DSCP: 32

    PD device, Power source: Unknown, Power Priority: Low, Wattage: 12.0

    Location - not advertised

 

  • Power TLV — Network connectivity devices and endpoints exchange power information. LLDP-MED provides information about how much power a device needs, power priority (for the switch to decide the order to allocate power to endpoints), and how a device is powered.

 

MED Information:

 

    MED Codes:

          (NP) Network Policy, (LI) Location Identification

          (PS) Power Source Entity, (PD) Power Device

          (IN) Inventory

 

    H/W revision: 14

    F/W revision: tnp45.9-3-1-CR17.bin

    S/W revision: SCCP45.9-4-2-1S

    Serial number: FCH1714A7PV

    Manufacturer: Cisco Systems, Inc.

    Model: CP-7945G

    Capabilities: NP, PD, IN

    Device type: Endpoint Class III

    Network Policy(Voice): VLAN 104, tagged, Layer-2 priority: 5, DSCP: 46

    Network Policy(Voice Signal): VLAN 104, tagged, Layer-2 priority: 4, DSCP: 32

    PD device, Power source: Unknown, Power Priority: Low, Wattage: 12.0

    Location - not advertised

 

Network Policy TLV

 

In case the network connectivity device (e.g. switch)  doesn't have a network policy configured, the network policy TLV will show the parameters received from the endpoint (e.g. IP Phone). These parameters might be assigned to the endpoint by different source (e.g. CUCM).

 

However, you can configure a network policy on the network connectivity device (e.g. switch) to be pushed to the endpoint using MED TLV. These parameters will override any other parameters assigned to the endpoint.

 

Important

 

While many Cisco IP Phones may support LLDP-MED, they do so only for VLAN and Power over Ethernet negotiation. Cisco IP Phones do not honor DSCP and CoS markings provided by LLDP-MED.

 

network-policy profile 1

 voice vlan 96 dscp 12

 voice-signaling vlan 96 dscp 13 ….. You can't assign different vlans to voice and signaling. If happened, the voice vlan will override the signaling vlan.

!

interface GigabitEthernet0/5

 network-policy 1

 

Note: If you assign a network policy to an interface, it will override the command 'switchport access voice vlan #'.

 

Location TLV

 

Location TLV can provide the following types of location information to endpoints:

 

  • 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: ELIN is a North America Dialing Plan (NADP) telephone number that may be used to represent one or more telephone extensions for the purpose of locating a caller who has dialed 911 from a Multi-Line Telephone System

 

location civic-location identifier 1

 building Test

 city Test

 country US

 floor 26

 primary-road-name "Silicon Valley"

!

location elin-location +6031112223 identifier Jakarta-Office

location admin-tag Jakarta-Office

!

interface GigabitEthernet1/1

 location civic-location-id 1

 location elin-location-id Jakarta-Office

 

Note that not all IP Phones support location TLV. You can verify this from the capabilities.

 

MED Information:

 

    MED Codes:

          (NP) Network Policy, (LI) Location Identification

          (PS) Power Source Entity, (PD) Power Device

          (IN) Inventory

 

    H/W revision: 14

    F/W revision: tnp45.9-3-1-CR17.bin

    S/W revision: SCCP45.9-4-2-1S

    Serial number: FCH1714A7PV

    Manufacturer: Cisco Systems, Inc.

    Model: CP-7945G

    Capabilities: NP, PD, IN

    Device type: Endpoint Class III

    Network Policy(Voice): VLAN 104, tagged, Layer-2 priority: 5, DSCP: 46

    Network Policy(Voice Signal): VLAN 104, tagged, Layer-2 priority: 4, DSCP: 32

    PD device, Power source: Unknown, Power Priority: Low, Wattage: 12.0

    Location - not advertised

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