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Tizzoncello75
Tizzoncello75
New Member
February 3, 2026
Question

Problem Forti-link

  • February 3, 2026
  • 6 replies
  • 583 views

Hi, i have two FG600F with version 7.4.11 and we use two MCLAG Switch ITER1 2048F connected with 25G GBIC interfate of FORTIGATE in port 7 and 8. We change the speed port and configure in 600F the port 5 to 8 in 25Gb speed setting. If we use in the ITER1 switch 2048F a version 7.2.x the fortilink is green and job. Any new software installed on the 2048F (7.4.7,7.4.8 or 7.4.9) from the GUI of FORTIGATE is completed but the fortilink going down and the interface used on FORTIGATE (7 and 8 in AGGREGATE CONFIGURATION and SPLIT disabled) and in the switch are down (but is present the light of laser in the port) What is for you the problem?

6 replies

AEK
SuperUser
AEK
SuperUser
February 4, 2026

Looks like a problem with link speed negotiation.

Try set both sides to auto-negotiate, or both to 25Gb, or both to 10Gb and see if it helps.

AEK
Tizzoncello75
Tizzoncello75Author
New Member
February 4, 2026

Hi we change the setting of port x5 at x8 in fortigate in 10G and change the configuration of fortiswitch in 10G with the command: FORTIGATE -> set ull-port-mode 10G FORTISWITCH -> config switch phy-mode - set port 37-48-phy-mode 10g and setting the auto in the port of fortiswitch: edit port 46 and 47 -> set speed auto-module. All other configuration are the same. In this case the 7.4.4 in the switch is ok for fortilink. IF we use the 25G and change the configuration setting of the port the fortilink is DOWN

AEK
SuperUser
AEK
SuperUser
February 4, 2026

Known issue:

1015698

On FortiGate 601F models, the X5 - X8 interfaces with 25G SFP28 DAC are down after upgrading to version 7.4.4 or later.

 

Ref:  https://docs.fortinet.com/document/fortigate/7.4.4/fortios-release-notes/236526

 

Resolved in 7.4.6.

Ref:  https://docs.fortinet.com/document/fortigate/7.4.6/fortios-release-notes/289806

 

So I recommend to update to 7.4.11 as it is the most stable of 7.4.x so far.

AEK
Tizzoncello75
Tizzoncello75Author
New Member
February 4, 2026

Hi thank you for the reply but we not use DAC cable ma simple SFP 25G model FORTINET FN-TRAN-SFP28-SR for FORTIGATE and for FORTISWITCH. In the fortigate we use the version 7.4.11 and in the fortiswitch with the 7.2.7 the fortilink at 25Gb is ok, with version 7.4.2,7.4.8,7.4.6 the fortilink is DOWN (but from tranciver we see the red laser present)

karolkrzyzyk
karolkrzyzyk
New Member
February 4, 2026

Did you checked status under CLI 

MahmutKarali
MahmutKarali
Explorer
February 4, 2026

Check the MC-LAG configuration to see if they are truly communicating with each other. You can check this by looking at the port section of the switches on Fortigate. For every 2 or more switches, all VLANs need to be visible to the relevant switches. Alternatively, you can try reconfiguring the Fortilink configuration. Disable split interface, keep ISL lockdown enabled, and also make sure the trunk ports' LLDP profiles are MC-LAG. -lag. You must do this via the CLI.


config switch-controller managed-switch

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