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+# VPP Link Layer Discovery Protocol (LLDP) implementation    {#lldp_doc}
+
+This is a memo intended to contain documentation of the VPP LLDP implementation
+Everything that is not directly obvious should come here.
+
+
+## LLDP
+LLDP is a link layer protocol to advertise the capabilities and current status of the system.
+
+There are 2 nodes handling LLDP
+
+1.) input-node which processes incoming packets and updates the local database
+2.) process-node which is responsible for sending out LLDP packets from VPP side
+
+
+### Configuration
+
+LLDP has a global configuration and a per-interface enable setting.
+
+Global configuration is modified using the "set lldp" command
+
+set lldp [system-name <string>] [tx-hold <value>] [tx-interval <value>]
+
+system-name: the name of the VPP system sent to peers in the system-name TLV
+tx-hold: multiplier for tx-interval when setting time-to-live (TTL) value in the LLDP packets (TTL = tx-hold * tx-interval + 1, if TTL > 65535, then TTL = 65535)
+tx-interval: time interval between sending out LLDP packets
+
+Per interface setting is done using the "set interface lldp" command
+
+set interface lldp <interface> | if_index <idx> [port-desc <string>] [disable]
+
+interface: the name of the interface for which to enable/disable LLDP
+if_index: sw interface index can be used if interface name is not used.
+port-desc: port description
+disable: LLDP feature can be enabled or disabled per interface.
+
+### Configuration example
+
+Configure system-name as "VPP" and transmit interval to 10 seconds:
+
+set lldp system-name VPP tx-interval 10
+
+Enable LLDP on interface TenGigabitEthernet5/0/1 with port description
+
+set interface lldp TenGigabitEthernet5/0/1 port-desc vtf:eth0
+
+
+### Operational data
+
+The list of LLDP-enabled interfaces which are up can be shown using "show lldp" command
+
+Example:
+DBGvpp# show lldp
+Local interface           Peer chassis ID           Remote port ID               Last heard      Last sent      Status
+GigabitEthernet2/0/1                                                               never         27.0s ago     inactive
+TenGigabitEthernet5/0/1   8c:60:4f:dd:ca:52         Eth1/3/3                     20.1s ago       18.3s ago      active
+
+All LLDP configuration data with all LLDP-enabled interfaces can be shown using "show lldp detail" command
+
+Example:
+DBGvpp# show lldp detail
+LLDP configuration:
+Configured system name: vpp
+Configured tx-hold: 4
+Configured tx-interval: 30
+
+LLDP-enabled interface table:
+
+Interface name: GigabitEthernet2/0/1
+Interface/peer state: inactive(timeout)
+Last known peer chassis ID:
+Last known peer port ID:
+Last packet sent: 12.4s ago
+Last packet received: never
+
+Interface name: GigabitEthernet2/0/2
+Interface/peer state: interface down
+Last packet sent: never
+
+Interface name: TenGigabitEthernet5/0/1
+Interface/peer state: active
+Peer chassis ID: 8c:60:4f:dd:ca:52(MAC address)
+Remote port ID: Eth1/3/3(Locally assigned)
+Last packet sent: 3.6s ago
+Last packet received: 5.5s ago
+