The ports on the SLC are always separate.
The SLC-5/04 and SLC-5/05 do have some limited "passthrough" capabilities. The CPU has to process every one of the messages, though, so the performance isn't good enough to be considered a "network bridge" like the Logix products.
You will have to read up in the User Manuals about the Status bits you have to set, and the Routing Table in the SLC-5/05.