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Vivus
Vivus
New Member
November 10, 2025
Question

The port does not come up when assembling LACP between FortiSwitch 1024E and 148F.

  • November 10, 2025
  • 2 replies
  • 508 views

Hello everyone.
I have five Fortinet devices:
1 x FortiGate 120G
2 x FortiSwitch 1024E (SW01-C and SW02-C)
2 x FortiSwitch 148F (SW03-A and SW04-A)

FortiLink is configured to manage switches on ports X1–X4, which are connected to ports 19 and 23 on the FortiSwitch 1024E.
I've also created an MCLAG between the two 1024Es on ports 25 and 26.
I'm currently trying to create an LACP connection between the core and access ports. The connections are as follows:
SW01-C port2 → SW03-A port49
SW01-C port17 → SW04-A port50
SW02-C port2 → SW04-A port49
SW02-C port17 → SW03-A port50
After connecting the patch cords, everything worked automatically, but port 49 on SW03-A doesn't work at all.
I've tried changing cables, ports, and settings—to no avail.
I'd appreciate any ideas or tips on where to look.
I'm attaching a screenshot of the diagram below.

 

WhatsApp Image 2025-11-10 at 11.31.46.jpeg

 

2 replies

Vivus
VivusAuthor
New Member
November 10, 2025

For clarity, I will add the configuration outputs:

SW01-C (trunk) # show
config switch trunk
edit "E24TF25003255-0"
set description "MCLAG-TO-SW02"
set mode lacp-active
set auto-isl 1
set mclag-icl enable
set members "port25" "port26"
next
edit "G120GTK25019861"
set description "Fortilink-TO-FG"
set auto-isl 1
set fortilink 1
set mclag enable
set members "port19" "port23"
next
edit "8FNTF25003610-0"
set mode lacp-active
set auto-isl 1
set mclag enable
set members "port17"
next
edit "8FNTF25002242-0"
set mode lacp-active
set auto-isl 1
set mclag enable
set members "port2"
next
end


SW02-C # show switch trunk
config switch trunk
edit "E24TF25003235-0"
set description "MCLAG-TO-SW01"
set mode lacp-active
set auto-isl 1
set mclag-icl enable
set members "port25" "port26"
next
edit "G120GTK25019861"
set description "Fortilink-TO-FG"
set auto-isl 1
set fortilink 1
set mclag enable
set members "port19" "port23"
next
edit "8FNTF25003610-0"
set mode lacp-active
set auto-isl 1
set mclag enable
set members "port2"
next
edit "8FNTF25002242-0"
set mode lacp-active
set auto-isl 1
set mclag enable
set members "port17"
next
end

SW03-A (trunk) # show
config switch trunk
edit "_FlInK1_MLAG0_"
set mode lacp-active
set auto-isl 1
set members "port49" "port50"
next
end

SW04-A # show switch trunk
config switch trunk
edit "_FlInK1_MLAG0_"
set mode lacp-active
set auto-isl 1
set members "port49" "port50"
next
end

 

AEK
SuperUser
AEK
SuperUser
November 11, 2025

Hi Vivus

I didn't touch this since a while, so I'll try to recall a little bit and I'll try to help, but I can do some mistake.

Here if I'm not wrong p2 and p17 should be part of the same LACP group in order to make them bot active at the same time. Otherwise spanning tree will disable one port. To make sure of that you can disconnect port 50 and you should see port 49 working fine.

AEK
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