Issue with VLANs in FortiLink and FSW – No DHCP on vlans

[Igneus]

Hello everyone,

I have a network that was configured a few years ago with a FortiGate (FG) using a "hardware switch" on ports 1, 2, and 3. The setup is as follows:

1. "internal1" interface:

   • Contains three VLANs:
     • VLAN 1: Used as the core VLAN (I know this is not ideal, but I am not authorized to change it).
     • VLAN 100: Network exclusively for wireless clients.
     • VLAN 1005: Network for phones.

2. Network topology:

   • FG -- Cisco Switch-- FortiSwitch 108 (FSW)
   • The FSW is connected to the FortiGate through "internal1."
   • I configured the FG to recognize and manage the FSW via FortiLink, even though it is not directly connected.

3. FortiLink configuration:

   • I created VLANs 100 and 1005 within FortiLink, assigning them IP addresses and DHCP servers different from those in "internal1."

Issue:
The VLANs configured on the FSW via FortiLink have no connectivity and do not receive IP addresses via DHCP.
I have already configured the ports on the intermediate switches (Cisco and HPE) to allow all VLANs, but the issue persists.

Any ideas on what might be missing or how to fix this? I appreciate any guidance.

Best regards.

[riteshpv]

Hi,

As I understand you are trying to setup FSW on Fortilink with Cisco switch in between.

This is not a recommended design for Fortilink L2 deployment.

1> Either you setup this FSW directly connected to FGT this is a L2 setup.

2> Or have Cisco connected between FSW with one FSW directly connected to FGT. Information in below link:

https://community.fortinet.com/t5/FortiSwitch/Technical-Tip-FortiLink-P2P-supported-network-topologi...

Regards,

Ritesh P V

[Igneus]

In this scenario, I have the option to connect FG directly to FSW. However, I face this issue—I need to 'share' VLANs between the Internal and FortiLink ports, using the same DHCP server and gateway. I don’t want to make my FortiGate configuration more complex than necessary.
is this possible?