Network Gateway

[Evan Sayer]

I am a little unsure of what hardware to buy for this network.

_______                        ______
|              |                        |              |                
            ______
|      A     |----------------> |      B     |------------------>  
|__C_|        ________
|______|                        |______|                              | 
| |--------->|       D     |
                                                              
|<----------------|  |               |______ |
                                                              |          
                  |
                                                              |          
                  |
                                                     ____|____           
       |_____
                                                      |                 
|                |              |
                                                      |         F      | 
                |      E     |
                                                      |_______ |         
        |______|

A is my cable modem, b is a freebsd gateway/natd/bind/httpd server 
(lot's of stuff, but most of them don't get too many requests; the 
webserver is very small).  I use natd's port redirection to give f and 
e the ability to be accessed from the internet via ssh and ftp.  F is 
the main file server, while E holds other unrelated files and is also a 
bakcup server for F.  E also does samba for another client i didn't put 
on there.  D is an unrelated lan.  You'll notice i have skipped c.  
This is because i don't know what to buy (router, switch, or hub).  I 
think when you run natd it acts as a firewall (the data under the 
gateway needs to be protected), but is it enough to warrant not buying 
a router?  I'm not sure how hubs or switches work.  Thanks a lot (i 
hope someone has an answer becuase these stupid drawings took me like 
an hour).