Stuart
Just to add to Collin's post. What you need is a router that supports NAT and pretty much all routers support NAT.
As an example lets say you have been allocated 195.17.17.0/28 which means you have useable IP addresses of 195.17.17.1 -> 195.17.17.14. The ISP will use one of these for their upstream router so a common setup would be
LAN -> R1 (wan interface 195.17.17.2/28) -> ( 195.17.17.1/28)ISP router -> Internet
So you now have 195.17.17.3 -> 195.17.17.14
With these address you can host your servers. So lets say you have a server with a private address of 192.168.5.10 and you want to present it to the Internet as 195.17.17.3
1) On R1 interface connecting to the subnet(s) where your servers reside
ip nat inside
2) On R1 interface connecting to ISP router -
ip nat outside
3) On R1
ip nat inside source static 192.168.5.10 195.17.17.3
4) Allow access to this server on specific ports with an access-list on the outside interface of R1 eg
access-list 101 permit tcp any host 195.17.17.3 eq 80
5) Apply access-list
R1 WAN interface
ip access-group 101 in
That is a rough idea of the sort of thing you will need at a basic level.
Jon
