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Link Layer Discovery Protocol

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

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

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

You can use the lldpcli 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. To disable LLDP on a single port, edit 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 and 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 4.1.0 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 4.1.0 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 4.1.0 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 4.1.0 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 4.1.0 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 4.1.0 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 4.1.0 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
----------------------------------------------------------------------
...

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)

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 -x"

Change CDP Settings

Cumulus Linux provides support for CDP so that the switch can advertise information about itself with Cisco routers that do not support LLDP. By default, the Cumulus Linux switch sends CDP packets only if the peer sends CDP packets. You can change this setting by replacing -c in the /etc/default/lldpd file with one of the following options:

Option Description
-cc The Cumulus Linux switch sends CDPv1 packets even when there is no detected CDP peer.
-ccc The Cumulus Linux switch sends CDPv2 packets even when there is no detected CDP peer.
-cccc The Cumulus Linux switch disables CDPv1 and enables CDPv2.
-ccccc The Cumulus Linux switch disables CDPv1 and forces CDPv2.

The following example changes the CDP setting to -ccc so that the switch sends CDPv2 packets even when there is no detected CDP peer:

cumulus@switch:~$ sudo nano /etc/default/lldpd
...
# Enable CDP by default
DAEMON_ARGS="-ccc -x -M 4"

You must restart the lldpd service for the changes to take effect.

cumulus@switch:~$ sudo systemctl restart lldpd

Caveats and Errata

  • Annex E (and hence Annex D) of IEEE802.1AB (lldp) is not supported.
  • If you configure both an eth0 IP address and a loopback IP address on the switch, LLDP advertises the loopback IP address as the management IP address. In this case, the Cumulus Linux switch behaves more like a typical Linux host than a networking appliance.