Hi!
Our internet connection here comes in via some CPE box, which when google the model number, basically is a managed switch. To this box I have my MikroTik router connected to one port and the TV box to another port. The MT gets a public IP from our ISP.
Now, since a MT router can do pretty much anything, I was thinking it would be nice to be able to get rid of the CPE box and just use my router. That is, connecting the cable that now connects to the WAN port on the CPE box, to the WAN port of the router and connect the TV box to one of the unused port on the router and by the magic of RouterOS, "simulate" the CPE box. I want this for two reasons; one, because it would make the setup much cleaner and get rid of a rather bulky box and two, save a few watts of electricity. This is what I've tested and figured out so far:
Router and TV box can be connected to any ports on the CPE box.
If I disconnect the incoming cable from the box and connect it directly to the WAN port of my router, internet works as just as it does with the CPE box, but I can obviously no longer watch TV.
If I test the CPE box internally in my own network as a regular switch, traffic flows to and from the WAN port and any of the LAN ports, but not between the LAN ports.

Now, VLAN's is one of those things I never learned and got a grip on, but given my findings above, I assume that the CPE box doesn't use any VLAN magic, but is basically just a regular switch, but with port isolation. I found a MikroTik article how to set up a bridge with port isolation, so I assume a "dirty" way of doing this would be to use three ports on the router, set up a bridge with port isolation on those ports and connect the incoming cable (the one normally connected to the WAN port of the CPE box) to one port, connect the TV box to another and just loop a short cable from the then "internet" port to the WAN port on the router. This wouldn't be very neat and I'm also one port short, since I'm already using three ports on the router, which is a 5 port hEX.
Could what I want to do be achieved?

All the best!

Internet + IPTV is usually a very complex setup, requiring a separate subnet, DHCP with specific options, VLANs and IGMP configuration. If the CPE box isn't causing you problems I'd recommend continuing to use it, while you can do IPTV over pure Mikrotik, the setup is complex and differs from ISP to ISP.

Well, I think I found an easy solution:) I tried replacing the CPE box with an ordinary switch I had and it worked! So I created a bridge in my router and tied port 1 (WAN) and port 5 (for TV box) to it and then connected the incoming cable to port 1 and TV box to port 5 and now it seems to work just fine.
Now, I don't have the port isolation, i.e. the isolation between the "internet" and TV ports that seemed to be configured in the CPE box, but I can't really see (with my limited knowledge) how that would be a problem, functionality or security wise. But please do correct me if I'm wrong here!

Internet + IPTV is usually a very complex setup, requiring a separate subnet, DHCP with specific options, VLANs and IGMP configuration. If the CPE box isn't causing you problems I'd recommend continuing to use it, while you can do IPTV over pure Mikrotik, the setup is complex and differs from ISP to ISP.

Well yes, I appreciate that. But in this case it does seem like it's probably not very complicated, given my findings and that my setup now works. But again, please correct me if it seems I've done something stupid here.

A thought for the future would be if it would be possible to connect the TV box on the LAN side and somehow forward the IPTV connection to it. This for cable routing purposes and that I also probably would learn a lot from it if I got such a setup working.

All the best!