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VLAN Switch setting caused managed switches to not work right

Just set up a 91G today, v7.0.14. Connected from port 1 to a managed switch reset to factory defaults (basically running as unmanaged at this point).

Devices on the switch would work at first when plugged in, but then couldn't get out to the Fortigate or the Internet. Sometimes I'd get some pings working, sometimes not. Anything connected directly to the Fortigate was fine. I almost got to thinking the switch was failing, until I tried an 8 port unmanaged Netgear and it didn't work either.

I had the LAN set up as the native VLAN on a VLAN switch tied to port 1. When I changed to software switch instead, everything worked perfectly. The only thing I can think is that VLAN switch tags all traffic where software switch does not tag the native VLAN, and I guess this tagging was confusing the switches. Not sure why it would confuse an old Netgear desktop unmanaged switch, but it did.

I pulled my hair for 2+ hours on this issue trying to figure out what was wrong with the switches when it wasn't the switches. Anyone have any further insight as to why this works this way? vshare
Contributor II

It sounds like you encountered an issue related to VLAN tagging and the behavior of your switches when connected to a VLAN-configured port on your Fortigate 91G. Let's break down the situation:

1. *VLAN Switch vs. Software Switch*: In Fortigate, when you set up a port as a VLAN switch, it means that the port will be part of a VLAN and will tag all traffic with the appropriate VLAN tag. On the other hand, when you set up a port as a software switch, it does not tag the native VLAN traffic. This difference in behavior can cause issues with devices that do not expect tagged VLAN traffic.

2. *Managed vs. Unmanaged Switches*: Managed switches are typically configured to handle VLAN tagging and other advanced network configurations. When you connected a managed switch to a port configured as a VLAN switch on the Fortigate, the switch might have been expecting tagged VLAN traffic. If the switch was reset to factory defaults, it might not have been configured to handle VLAN tagging properly, leading to connectivity issues.

3. *Old Netgear Desktop Unmanaged Switch*: Even though the Netgear switch is unmanaged, it is possible that it was somehow affected by the tagged VLAN traffic coming from the Fortigate. Unmanaged switches usually pass traffic through without any modification, but in this case, the tagged traffic might have caused confusion or disruptions in the network.

In your scenario, switching the port to a software switch likely resolved the issue because it stopped tagging the traffic with VLAN information, allowing the switches to communicate properly without the confusion caused by tagged traffic.

If you need to use VLANs in your network setup, make sure that all devices connected to VLAN-configured ports can handle tagged VLAN traffic or configure the ports appropriately to match the capabilities of the connected devices. Additionally, double-check the configurations on your managed switches to ensure they are set up correctly for your network requirements.

If you have any specific questions or need further assistance with your network setup, feel free to provide more details!

Thanks & Regards,
Faizal Emam
Thanks & Regards,Faizal Emam

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