You don't necessarily need a router in a network configuration if you have only one segment.
I am not sure I understand "only one segment." I would love it if I did not have to have a router and could connect the cable modem directly to the switch. After all, the server is the DHPS. The router is the one thing that I have had to replace more often than anything else at work. Then again, as you say, I got what I paid for it. I guess the reason I use it is because it is easy to use (I have one at home, never gives me problems) and I know how to configure it. Thanks for taking the time to help me.
The only time you would need a router is if you have a WAN (Internet) connection that is anything other than Ethernet like a T1. Cable and DSL modems will hand off an Ethernet connection which is why you can connect them directly to your home computer and computer away. You may be happy with ZA or Windows Firewall or you may purchase a hardware/firewall. Many inexpensive routers come with decent firewalls for home use.
Most good firewalls have what we term NAT or network address translation. NAT allows all of your private IPs on your LAN such as 192.168.0.5 through 15 let's say to share one IP from your ISP so you don't have to purchase multiple IPs. The firewall will also block packets which it is set up to not allow through hence the term firewall.
So, you would have something like:
ISP --> modem --> firewall -- switch (or use ports on firewall or router) --> clients and server
That is with cable or DSL modem
With T1 or frame relay with involves PPP or frame-relay encapsulation, you would need a router to route that across to the Ethernet interface.
Internet --> T1 --> Router (without firewall) --> firewall -- switch -- private clients and server
Routers are designed to get packets from one place to another as fast as possible. Firewalls are designed to block all packets and to carefully inspect all packets usually via stateful inspection for stuff you don't want.
There are hybrids of both. You will see many of these with the inexpensive Netgears and Linksyses.
DISCLAIMER: There are many other configurations such as using two or three network cards on your server, etc. which can get more complicated.
But, the bottom line is, given your setup, it is not always necessary to use a router AND a firewall and, if one is capable of doing both, you have a better chance of running into networking problems.
Subnets such as 192.168.0.1/24 and 192.168.1.1/24 allow you basically divide groups into different networks. With small LANs such as what most of us run, it is not necessary. But, in a company such as Google, where you have Accounting, R & D, Billing, etc. you may not want each group to have access to each other. Therefore you put them on small segments of a larger network, hence the term "subnet." This will usually require a router to direct traffic to the different subnets.
