Options to pass a VLAN through different Fortigate interfaces in NAT mode

Question

Hello team!!!

I hope it goes well for you!

We have 2 different "trunk" interfaces (With different VLANs on each one).

For example:

* VLANs 10, 20 and 30 on port1

* VLANs 40, 50 and 60 on port2

Now, we need to add the VLAN 100 in both trunks interfaces

Because, for example, we need to access from something in VLAN 100 connected to port1 to something on VLAN 100, connected to port2.

We have a managed switch directly connected to port1 and a different managed switch connected to port2

I thought to create the first VLAN Switch (Other 2 are not VLAN switches, just interfaces with VLANs) but I do not believe I will be able to use current port 1 and port 2 on it

So, with my moderate knowledge, I think the following 2 options:

* Create a VLAN switch for different ports (example: port3 and port4), with VLAN 100, and connect both to each managed switch in a different port, with VLAN 100 as tagged

* Create a virtual switch (without VLANs) for different ports (example: port3 and port4), and connect both to each managed switch in a different port, with VLAN 100 as untagged

I think these 2 options are not so prolix.

Is there other option?

What do you suggest?

Thanks in advance.

Regards,

Damián

atakannatak · Accepted Answer

Hi @damianhlozano ,You can only create one interface on FortiGate with the same VLAN-ID value, so in this scenario, it would be the best scenario to combine two of the solutions you mentioned according to your topology. For this, based on your topology, I configured a software switch definition on port 3/4 and then created a new interface under this definition with VLAN-ID 100. Then I created 2 different client machines on two different switches and tested end-to-end accesses and I did not encounter any problems. If you design this way, you will have flexibility if you have similar needs in the future. For example, a new interface can be created for VLAN-ID 200 using the same software switch.  BR. If my answer provided a solution for you, please mark the reply as solved it so that others can get it easily while searching for similar scenarios.

damianhlozano · Answer

Hello, Just to know before try this, just if you already know the answer:Should this work without any rule to allow traffic, right? (In layer 2, like a switch) ThanksRegards

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