Soccerman: Sort of. A switch has a CAM table which caches machine locations for a certain period after that machine sends a packet on that subnet. A router has an routing table that tells it where to route packets. Both direct traffic to the correct port. The main difference is a router has the concept of subnets while plain switches have no concept of subnets. When you send a packet to the broadcast address on one of the ports on the switch it goes out all the ports. When you send a packet to the broadcast address and a router sees it, the router generally ignores it (I'm not going to get into the situations where it would be configured otherwise.)
A switch gets the info on what machines are where by building a CAM table by watching the Data Link layer and watches the source MAC address. When a switch receives a packet with a source MAC of foo and a destination MAC of bar. It records that foo is on the port it just received the packet for. Then it checks its CAM table to see if it has a record for bar. If bar is not in its CAM table, it sends the packets out all the ports.
A router on the other hand has a routing table and a default gateway. When a router receives a packet it looks at the Network layer and looks at the IP source and destination. It also keeps track of ARP packets to watch which port machines are on. If its routing table tells it which port to send a packet to it does so. If its routing table does not have the info it checks its ARP table to see if it can determine the best port. There are also protocols like BGP that can also influence this decision as to what the best route is. Otherwise, it sends the packet to the default gateway.
Hopefully, that helps. If you need more technical than that I will need to get my SO onto this thread. I'm just a sysadmin not a network person. I'm a computer geek, she's a network geek. I know enough networking to determine if the network is causing problems with my machines. She knows enough about computers to determine if a computer is causing problems with her network
oldfart:
Correct, the Netgear RT31x connects to a DSL modem on one side and your LAN on the other. Both with RJ45 ethernet connections. The Cisco performs the tasks of a DSL/ethernet router. It has an RJ11 phone connector on one end and an RJ45 on the other. Cisco has various models for the various types of DSL. Check there website for which model is for which xDSL. If you ever change ISPs and also change what type of DSL technology you use, you would need a new Cisco.
tommyc:
One uses an FS108 or some other hub or switch if their Router has a single port for the LAN. If you used a Netgear RT311 for example you would need a hub or switch for your LAN if you were connecting to more than one machine (One machine you could use a crossover cable.) If you had an RT314 as long as you have enough ports on the RT314 you just connect one machine to each port on the RT314. The RT314 performs the tasks of both the router and the switch. The RT314 has 4 ports. The FS108 has 8. I have both a 4 port hub in one room and an 8 port switch (FS108) in another other. My DSL modem connects to my router/firewall which then connects to my FS108 which then uses the crossover port and a normal patch cable to hook up to the 4 port hub.
That is another thing, some hubs and switches have one port that is either dedicated or togglable between straight through and cross-over. If you look at the picture on Netgears website of the FS104/FS108 you will see a black button on the far right. That button toggles between straight through and crossover. That port can be used to chain switches and hubs together with normal patch cables. You can also chain hubs and switches together with a non cross-over port and a cross-over cable. If you want to get really odd I had a friend whose hub had a dedicated crossover port (not togglable) and used a crossover cable to hook it up to a machine (cross-over + cross-over = straight through).
One mistake I often see people make: Some old hubs will have two ports on one side and one will be marked cross-over and the hub will have one more port than it advertises physically. For example a 4-port hub with 5-ports. Only one of those two ports can be used at the same time, if you want straight-through you use the straight-through, and if you want cross-over you use cross-over. But, not both at the same time. I think this is why companies are moving away from that and two the button. I'm sure they got a lot of tech support phone calls from people trying to use both ports. This one or the other port is still common on the $20 hubs you find at the local computer store. RTFM.
The RT314 should be good for you. You would hook up the DSL modem to one side and your two or three computers to the other. The RT314 can do NAT and simple firewalling.
If you want to be able to support more than 4 machines, I would get the RT311 and an FS108.
If you are getting enough IPs from your ISP that each of your machines can have a real IP, you may not need a router at all. One could just plug in a hub or switch (like the FS108) directly to the DSL modem and then use real IPs on each machine.
By real IPs I mean Internet addressable. For NAT you use non Internet addressable IPs such as the 10., 172.16, or 192.168.0 ranges. These are generally referred to as the unassigned ranges.
My set-up at home is really odd since I have 9 addressable IPs (2 for the router/firewall -- one internal and one external) The Internal network is both the addressable 8 IPs (6 usable, 1 network/old Sun broadcast, and 1 broadcast) and an entire unassigned subnet. Some machines internally can be addressed from the Internet others can not. If someone comes over they tell Windows to use DHCP and the Linux box assigns them an IP from the unassigned range, they are NATed and can access the Internet from my house.
Zone Alarm is a free (for non-commercial use) firewall program for Windows. You install it on a Windows box and it asks you what network traffic is O.K., and what isn't. It is very easy to use. I've been fiddling with it on the box I'm on right now. So right now I'm behind two firewalls I actually found out about its existance on the forums here, so if you do some searches on the forums you can find out more about it. It is available at
http://www.zonelabs.com/ I here it gives a lot of false alarms, but that isn't my experience for obvious reasons (Hint: The first firewall is blocking them all.) So maybe I like it because I haven't experienced the worst part of it. However, you can disable the notifying you of alarms completely. So if you the notifaction gets anoying you can disable it.
I appologize if this message was either too technical or not technical enough. I was just trying to give enough info for you to have an idea on various set-ups. Just ask for clarification if you need it.