everything else being equal - you SHOULD be able to connect directly through the SLC-5/05's Ethernet port ...
but ...
it's usually easier to connect through the processor's DB9 port FIRST using a null-modem cable and the RS232/DF1 driver in RSLinx ... this is usually the easiest way to set the IP address for the Ethernet port ...
then once the Ethernet port has been set up, the rest of the connection process should be relatively easy ...