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GusZ
Staff
GusZ
Staff
June 15, 2026

Technical Tip: improving FortiGate resilience and resources utilization by using LLDP-based FortiSwitch detection

  • June 15, 2026
  • 0 replies
  • 169 views

Description

This article describes why and how to reconfigure FortiGate devices to detect FortiSwitches units using LLDP.

Scope

FortiOS, FortiSwitch.

Solution

FortiOS provides two distinct neighbor discovery mechanisms to detect FortiSwitches units:

  • FortiLink: the original, Fortinet-proprietary method.

  • LLDP (Link Layer Discovery Protocol): an IEEE standard (802.1AB-2005), latest addition (FortiOS LLDP support is also available for other products such as FortiAP and FortiVoice).


LLDP is supported in recent FortiOS versions and, starting with FortiOS 7.6.1, it is now the default FortiSwitch neighbor discovery mechanism. In comparison with FortiLink, the Fortinet LLDP implementation has a number of advantages, specially regarding resources utilization.

Replacing FortiLink with LLDP is recommended, in order to improve FortiGate resilience and resources utilization (in some extreme circumstances, FortiLink setups can lead to high consumption of resources, which in turn may cause outages).

It is important to mention that, when upgrading to FortiOS 7.6.1 or above, the migration process with not automatically replace FortiLink with LLDP (only new configurations will use LLDP by default). This change has to be done manually by an administrator as described below:

config system interface
    edit fortilink
        set lldp-reception enable
        set lldp-transmission enable
        set fortilink-neighbor-detect lldp
    next
end


Depending on multiple factors, replacing FortiLink with LLDP may cause a service disruption (between 2 and 60 seconds on average). Therefore, it is recommended to apply the changes during a maintenance window (e.g. during a firmware upgrade).

If the FortiGate unit is also managing FortiAP devices, it is also recommended that all wireless profiles are LLDP enabled:

config wireless-controller wtp-profile
    edit <WTP_PROFILE_NAME>
        set lldp enable         <----- default value since FortiOS 6.2.2


Related documents:

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