Connecting 2 networks to one Internet connection

I currently have a small business network using a Linksys WAG54G

I want to create another network linking to the internet through this
gateway but ensure that the 2 networks are invisible to each other.

I have read various threads and the simplest way would appear to be to
have three routers in total, one for the internet connection and one
each for the 2 networks I want to create.

I already have an additional router, a Linksys WRT54G and is it
possible to achieve the same thing with just 2 routers? I would prefer
to avoid the expense and clutter of a third router if possible.

When I plug the WAG54G ADSL router into the WAN port of the WRT54G I
can have a seperate address range which works fine for Internet access
but the network on the WRT54G can still see the network on the
WAG54G.....is this inevitable or is there some way of hiding the
networks from each other using the routing functions?

Martin.

Haven't actually tried this, but have done some similar stuff. Can you
set the gateway of the second router to the ISP gateway? Usually,
you'd set it to the first router's address -- then you'd see its
members.

What are the settings for the two networks? Unless they're different
nets (e.g. 192.168.1.x and 192.168.2.x), they'll definitely see each
other.

As you can see, I'm groping and could use a bit more info. Hope
someone else has actually done what you're trying.