Hello.

I am somehow new in the Linux field. I searched on internet for this issue, but I could not find a similar case.

My network is simple:

ISP -> Switch_1 (with management) -> Linux router -> switch -> servers

Till now, my ISP provided me internet on tagged vlans, so on Switch_1 I setup tagged vlan on incoming port and outgoing port (that connects the Linux router). In the Linux router, i setup subinterface with vlan (like ethx.id and IP/subnet). Everything was fine...

Now, my new ISP gives me internet with untagged port, but with VLAN.

I setup on Switch_1 (non-cisco) incoming/outgoing ports with untagged vlan...and on the Linux router I tried both ways: vlan as ethx.id and non-vlan ethx.

Both ways failed. I read something about bridge...but..Is there any way to handle this situation?

Thank you

From my point of view, I think you should remove Switch_1 and connect ISP to Linux router.
Then create a default interface without VLAN. After that you will have to make the NAT part on the new interface.
I think you`re LAN network sould be a transparent one if the ISP transports a untagged VLAN.