Hows it going everyone?

I just have a question about networks.
I was doing a bit of footprinting on the local businesses (a WAN i suppose)
in my area and i found that a lot of them are on the one isdn network
(we dont have broadband).

from 1.2.3.0 --1.2.3.255 as an example this is the size not the actual i.ps

Using a tool call networkview i mapped them out.

Just have 2 questions really.

1:Networkview identified some of them as servers and others as not a "snmp device".
What does this mean?
Does this mean some have a network behind the 1 i.p. and the others are just one
computer maybe?

2:More importantly,i would be interested if anyone knows how people discover the i.ps
of the many computers in these businesses from knowing the 1 i.p. address of the server.
Some of these business have maybe 20 computers with maybe open shares but how do
you know the location of these machines from knowing their 1 i.p. number on the isdn network.

This could be a piece of cake for some of ye.
looking forward to hear what ye think.