Hi,

I have tried to find this information but I couldn't find it so I will try to post a topic in here instead.

I have a rb450g which I want to use as following

Port 1: WAN Interface / Gateway for internal bridge -ok
Port 2-4: Bridged ports -ok
Port 5: Separate port that should just forward all traffic to a specific host.

In other words I need Port 5 to be working as a switchport. The connected host is running dhcp and should get an IP from the ISP using that interface.

For some reason I can't manage to make Port 5 working as I want. I don't want the interface to grab an IP.

Can anyone please help my with this beginner issue?

Regards,
Tony

What do you mean by "I do not want the interface to grab an IP"?

Are you only running IP traffic on port 5?

What device(s) are connected to port 5? I recommend adding an IP and DHCP to port 5 in a unique IP range then add a DST-NAT firewall rule to all traffic matching that source range to dst-nat it to the host you want all traffic to go to.

Set the DHCP to make the mask=32 or subnet 255.255.255.255. Then all traffic will be directed to the default gateway (being the IP of port 5 on your Mikrotik Router). This works on Windows PCs, but I have found the 32bit subnet not to work on Linux hosts.

Hosts connected to port 5 have to use the DHCP or have the IP of port 5 on your mikrotik set as the default gateway.

If I understood you correctly, it sounds like you just want to bridge ports 1 and 5 together? In which case, do so; you will need to create another bridge. (and you should move any configuration on port 1 to be on that bridge instead).