This documentation is for the extended support release (ESR) version of Cumulus Linux. We will continue to keep this content up to date until 21 February, 2023, when ESR support ends. For more information about ESR, please read this knowledge base article.

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Link Layer Discovery Protocol

The lldpd daemon implements the IEEE802.1AB (Link Layer Discovery Protocol, or LLDP) standard. LLDP enables you to know which ports are neighbors of a given port. By default, lldpd runs as a daemon and is started at system boot. lldpd command line arguments are placed in /etc/default/lldpd. lldpd configuration options are placed in /etc/lldpd.conf or under /etc/lldpd.d/.

For more details on the command line arguments and config options, see man lldpd(8).

lldpd supports CDP (Cisco Discovery Protocol, v1 and v2). lldpd logs by default into /var/log/daemon.log with an lldpd prefix.

lldpcli is the CLI tool to query the lldpd daemon for neighbors, statistics, and other running configuration information. See man lldpcli(8) for details.

Configure LLDP

You configure lldpd settings in /etc/lldpd.conf or /etc/lldpd.d/.

Here is an example persistent configuration:

cumulus@switch:~$ sudo cat /etc/lldpd.conf
configure lldp tx-interval 40
configure lldp tx-hold 3
configure system interface pattern *,!eth0,swp*

The last line in the example above shows that LLDP is disabled on eth0. You can disable LLDP on a single port by editing the /etc/default/lldpd file. This file specifies the default options to present to the lldpd service when it starts. The following example uses the -I option to disable LLDP on swp43:

cumulus@switch:~$ sudo nano /etc/default/lldpd

# Add "-x" to DAEMON_ARGS to start SNMP subagent
# Enable CDP by default
DAEMON_ARGS="-c -I *,!swp43"

lldpd has two timers defined by the tx-interval setting that affect each switch port:

  • The first timer catches any port-related changes.
  • The second is a system-based refresh timer on each port that looks for other changes like hostname. This timer uses the tx-interval value multiplied by 20.

lldpd logs to /var/log/daemon.log with the lldpd prefix:

cumulus@switch:~$ sudo tail -f /var/log/daemon.log  | grep lldp
Aug  7 17:26:17 switch lldpd[1712]: unable to get system name
Aug  7 17:26:17 switch lldpd[1712]: unable to get system name
Aug  7 17:26:17 switch lldpcli[1711]: lldpd should resume operations
Aug  7 17:26:32 switch lldpd[1805]: NET-SNMP version 5.4.3 AgentX subagent connected

Example lldpcli Commands

To show all neighbors on all ports/interfaces:

cumulus@switch:~$ sudo lldpcli show neighbors
-------------------------------------------------------------------------------
LLDP neighbors:
-------------------------------------------------------------------------------
Interface:    eth0, via: LLDP, RID: 1, Time: 0 day, 17:38:08
  Chassis:     
    ChassisID:    mac 08:9e:01:e9:66:5a
    SysName:      PIONEERMS22
    SysDescr:     Cumulus Linux version 2.5.4 running on quanta lb9
    MgmtIP:       192.168.0.22
    Capability:   Bridge, on
    Capability:   Router, on
  Port:        
    PortID:       ifname swp47
    PortDescr:    swp47
-------------------------------------------------------------------------------
Interface:    swp1, via: LLDP, RID: 10, Time: 0 day, 17:08:27
  Chassis:     
    ChassisID:    mac 00:01:00:00:09:00
    SysName:      MSP-1
    SysDescr:     Cumulus Linux version 3.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.9
    MgmtIP:       fe80::201:ff:fe00:900
    Capability:   Bridge, off
    Capability:   Router, on
  Port:        
    PortID:       ifname swp1
    PortDescr:    swp1
-------------------------------------------------------------------------------
Interface:    swp2, via: LLDP, RID: 10, Time: 0 day, 17:08:27
  Chassis:     
    ChassisID:    mac 00:01:00:00:09:00
    SysName:      MSP-1
    SysDescr:     Cumulus Linux version 3.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.9
    MgmtIP:       fe80::201:ff:fe00:900
    Capability:   Bridge, off
    Capability:   Router, on
  Port:        
    PortID:       ifname swp2
    PortDescr:    swp2
-------------------------------------------------------------------------------
Interface:    swp3, via: LLDP, RID: 11, Time: 0 day, 17:08:27
  Chassis:     
    ChassisID:    mac 00:01:00:00:0a:00
    SysName:      MSP-2
    SysDescr:     Cumulus Linux version 3.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.10
    MgmtIP:       fe80::201:ff:fe00:a00
    Capability:   Bridge, off
    Capability:   Router, on
  Port:        
    PortID:       ifname swp1
    PortDescr:    swp1
-------------------------------------------------------------------------------
Interface:    swp4, via: LLDP, RID: 11, Time: 0 day, 17:08:27
  Chassis:     
    ChassisID:    mac 00:01:00:00:0a:00
    SysName:      MSP-2
    SysDescr:     Cumulus Linux version 3.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.10
    MgmtIP:       fe80::201:ff:fe00:a00
    Capability:   Bridge, off
    Capability:   Router, on
  Port:        
    PortID:       ifname swp2
    PortDescr:    swp2
-------------------------------------------------------------------------------
Interface:    swp49s1, via: LLDP, RID: 9, Time: 0 day, 16:55:00
  Chassis:     
    ChassisID:    mac 00:01:00:00:0c:00
    SysName:      TORC-1-2
    SysDescr:     Cumulus Linux version 3.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.12
    MgmtIP:       fe80::201:ff:fe00:c00
    Capability:   Bridge, on
    Capability:   Router, on
  Port:        
    PortID:       ifname swp6
    PortDescr:    swp6
-------------------------------------------------------------------------------
Interface:    swp49s0, via: LLDP, RID: 9, Time: 0 day, 16:55:00
  Chassis:     
    ChassisID:    mac 00:01:00:00:0c:00
    SysName:      TORC-1-2
    SysDescr:     Cumulus Linux version 3.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.12
    MgmtIP:       fe80::201:ff:fe00:c00
    Capability:   Bridge, on
    Capability:   Router, on
  Port:        
    PortID:       ifname swp5
    PortDescr:    swp5
-------------------------------------------------------------------------------

To show lldpd statistics for all ports:

cumulus@switch:~$ sudo lldpcli show statistics
----------------------------------------------------------------------
LLDP statistics:
----------------------------------------------------------------------
Interface:    eth0
  Transmitted:  9423
  Received:     17634
  Discarded:    0
  Unrecognized: 0
  Ageout:       10
  Inserted:     20
  Deleted:      10
--------------------------------------------------------------------
Interface:    swp1
  Transmitted:  9423
  Received:     6264
  Discarded:    0
  Unrecognized: 0
  Ageout:       0
  Inserted:     2
  Deleted:      0
---------------------------------------------------------------------
Interface:    swp2
  Transmitted:  9423
  Received:     6264
  Discarded:    0
  Unrecognized: 0
  Ageout:       0
  Inserted:     2
  Deleted:      0
---------------------------------------------------------------------
Interface:    swp3
  Transmitted:  9423
  Received:     6265
  Discarded:    0
  Unrecognized: 0
  Ageout:       0
  Inserted:     2
  Deleted:      0
----------------------------------------------------------------------
... and more (output truncated to fit this document)

To show lldpd statistics summary for all ports:

cumulus@switch:~$ sudo lldpcli show statistics summary
---------------------------------------------------------------------
LLDP Global statistics:
---------------------------------------------------------------------
Summary of stats:
  Transmitted:  648186
  Received:     437557
  Discarded:    0
  Unrecognized: 0
  Ageout:       10
  Inserted:     38
  Deleted:      10

To show the lldpd running configuration:

cumulus@switch:~$ sudo lldpcli show running-configuration
--------------------------------------------------------------------
Global configuration:
--------------------------------------------------------------------
Configuration:
  Transmit delay: 30
  Transmit hold: 4
  Receive mode: no
  Pattern for management addresses: (none)
  Interface pattern: (none)
  Interface pattern blacklist: (none)
  Interface pattern for chassis ID: (none)
  Override description with: (none)
  Override platform with: Linux
  Override system name with: (none)
  Advertise version: yes
  Update interface descriptions: no
  Promiscuous mode on managed interfaces: no
  Disable LLDP-MED inventory: yes
  LLDP-MED fast start mechanism: yes
  LLDP-MED fast start interval: 1
  Source MAC for LLDP frames on bond slaves: local
  Portid TLV Subtype for lldp frames: ifname
--------------------------------------------------------------------
Runtime Configuration (Advanced)

A runtime configuration does not persist when you reboot the switch - all changes are lost.

To configure active interfaces:

cumulus@switch:~$ sudo lldpcli configure system interface pattern "swp*"

To configure inactive interfaces:

cumulus@switch:~$ sudo lldpcli configure system interface pattern *,!eth0,swp*

The active interface list always overrides the inactive interface list.

To reset any interface list to none:

cumulus@switch:~$ sudo lldpcli configure system interface pattern ""

VLAN (dot1) TLV

LLDPD in Cumulus Linux is compiled to not share VLAN information with peers. Cumulus Linux 3.7.11 and later provides the VLAN (dot1) TLV runtime option to enable advertisement of VLAN TLVs to LLDP peers.

To enable the VLAN (dot1) TLV option, run the following command:

cumulus@switch:~$ sudo lldpcli configure lldp dot1-tlv

Alternatively, you can add the configure lldp dot1-tlv line to the /etc/lldpd.d/README.conf file, then restart lldpd.

When enabled, you see DOT1 TLV advertise: yes in the sudo lldpcli show running-configuration command output:

cumulus@switch:~$ sudo lldpcli show running-configuration
----------------------------------------------------------
Global configuration:
----------------------------------------------------------
Configuration:
  Transmit delay: 30
  Transmit hold: 4
  Maximum number of neighbors: 32
  ...
  DOT1 TLV advertise: yes
  ...

The following example shows the lldpctl show neighbors command output when the VLAN (dot1) TLV option is enabled:

cumulus@switch:~$ sudo lldpctl show neighbors
-------------------------------------------------------------------------------
LLDP neighbors:
-------------------------------------------------------------------------------
Interface:    swp4, via: LLDP, RID: 17, Time: 0 day, 00:04:32
  Chassis:
    ChassisID:    mac 52:54:00:f1:f4:2a
    SysName:      leaf04
...
  VLAN:         10, pvid: yes
...

To disable the VLAN (dot1) TLV option, run the lldpcli unconfigure lldp dot1-tlv command. When disabled, the sudo lldpcli show running-configuration command output shows DOT1 TLV advertise: no.

Scale Considerations

The number of VLAN TLVs that an LLDP frame can contain depends on the interface MTU and the number or other organizational TLVs. Because Cumulus Linux does not fragment LLDP frames, if the LLDP frame size (inclusive of all VLAN TLVs) exceeds the MTU, frames are dropped, which leads to an LLDP peering failure.

Use the following as guidance:

  • With an interface MTU of 1500 bytes, LLDP frames can carry approximately 50 VLAN TLVs.
  • With an interface MTU of 9216 bytes, LLDP frames can carry approximately 350 VLAN TLVs.

If you enable the VLAN (dot1) TLV option with a high number of VLANs resulting in LLDP frames that are larger than the MTU, the frames are dropped and following message is recorded in /var/log/syslog:

2019-12-09T00:23:39.183653+00:00 act-5812-11 lldpd[8585]: Cannot send LLDP packet for swpX, Too big message

Enable the SNMP Subagent in LLDP

LLDP does not enable the SNMP subagent by default. You need to edit /etc/default/lldpd and enable the -x option.

cumulus@switch:~$ sudo nano /etc/default/lldpd

# Add "-x" to DAEMON_ARGS to start SNMP subagent

# Enable CDP by default
DAEMON_ARGS="-c"

Caveats and Errata

  • Annex E (and hence Annex D) of IEEE802.1AB (lldp) is not supported.