Question : Connecting Cisco Router/Switch/Cable Modem?

I have a Cisco 2900 switch and 2501 router; how do I connect the router to the switch and the router to my Cable modem with only 1 Ethernet and 2 Serial ports?

Answer : Connecting Cisco Router/Switch/Cable Modem?

What model of cable modem do you have?  Most likely it does not have any NAT/PAT or "firewall" features.  If you just use your cable modem and the Cisco switch, you will probably only have a single IP address to use and not have any NAT/PAT.   NAT/PAT is required if you want to have more than one PC connected to the Internet.  NAT/PAT is probably the number one thing you can do to protect your network.  

The 2501 router is not going to be of much use with just a single ethernet interface.  The 2514 router has two ethernet interfaces and could be used.

Your least expensive solution to provide NAT/PAT and firewalling features would be to purchase a Linksys or similar router/firewall.

pc---switch----router-----cable modem------Internet

Hope this helps!