I'll risk being wrong just to see if the parrots can come up with the right answer.
The Westall modem has marking on the plugs as e1 - e4 but these are not really NIC, they are ports and you simple plug in the several computers and do internet sharing with each geting a new 192.168.1.nnn ip.
Yes no? According to your specs you are get 192.168.2.nnn which would make the above false and every shared commputer would be a completely seperate sub-net.
Since 192.168. is a no routable ip set you must be correct.
And all the so called router brainiacs are shooting blanks.
Whch way does it really work?
Maybe it depends on the way the router was mfg'ed and the ISP and wheather they control it or you control it.
Life is fun, but complex.
OK, come on in experts.