redrumloa:
I know you want to use what you have on hand
but the very easiest and 99% working way is
to (what some other user here told you) use a
simple 10/100 switch.
I have one router at home and below that I have
one 8 port switch. All internal traffic only uses
the switch and never makes that sad router
crawl on knees

I connected them both using a cross-over TP.
It worked like a charm - I did not have to change
any IP settings on any of the machines and they all
kept the same IP assigned from the router's DHCP.
The switches are very cheap; 4 ports for like 30USD
and 8 ports for maybe 50.