Most common use of a home router is ofcourse NAT. The “new” 2621 is now running IOS 12.3.26(GD) IP and has been fully configured for NAT. There are lots of guides out there but I will post my own approach here also:
conf terminal
interface fastethernet 0/0no shutdown
description WAN
bandwidth 102400
ip address xxx.xxx.xxx.xxx 255.255.255.248
ip nat outside
interface fastethernet 0/1
no shutdown
description LAN
bandwidth 102400
ip address xxx.xxx.xxx.xxx 255.255.255.0
exit
access-list 1 permit xxx.xxx.xxx.xxx 0.0.0.255
ip nat inside source list 1 interface fastethernet 0/0 overload
Ofcourse this scenario does assume you have made no settings in the router what-so-ever but you can always leave out anything you don’t need. I also used an access-list for added security internally.