I have cisco 2501 router, a cisco 1912c switch,a dsl modem and four computers.I need help.I am a newbie what port do I use to connect the router to the modem or switch.or better stated how can I configure this to make my own network i would like to set up a server and have all my computers share and access files and dsl connection. do I need any special cables besides cat5. Please help.

I dont mean to be rude just completely truthful, the set up is a little involved. To give you a kind of an overview. The model router you are talking about doesn't use a modem for it's serial connection, it's designed for branch offices, and therefore branch office level support. The serial connection is the connection the router makes to the WAN (Internet). The way it generally works is, a line (T1, 56k/64k, etc.) would first connect to a DSU/CSU (data service unit/channel service unit) - acts as a "modem" on digital lines. The DSU/CSU connects to the routers serial port (either 1 or 2). I can imagine you have been trying to figure out how in the world that cable is to connect in your dsl modem (LOL). Then you have to connect the Ethernet port of the router to the switch. Because you have a 2501 you need what is called an AUI (attachment unit interface). One side of the AUI will have the DB-15 required to plug into the router, and the other end will have an RJ-45 (Cat 5). You would connect from there to any port on the front of your switch. The computers can connect to any port on your switch in the front. Recommendation - If you want to use a router, rather than using overkill, which is going to cost you (you have to buy the DSU/CSU, not going to operate on DSL, and the proper AUI), buy a Cisco 1600, it's a more ideal solution for you. I've include the web page, with color pictures in the link I have listed under Optional Link URL. It is designed (if you buy the right one) to take in DSL, and all you need is RJ-45 (Cat 5) to connect from the router to the switch, you can even ditch the dsl modem. However, an even better solution is if you load your computers with W2k or WXP, then you dont need the router at all. You can configure one of the computers as a server and domain controller, which would allow all your computers to share files, print, etc., and it has ICS (Internet Connection Sharing), to allow all your computers to share access to the internet. I just gave you the hardware stats. There is a lot more involved in configuring both the Cisco equipment, and the Computers to make it all work. If you live in Atlanta, I charge $15/15 min. Configure your microsoft and cisco equipment.

Well considering you already have this equipment you can set up, with some insight, experience, and lot's of experimentation, what you seek. As said in the last post there is more to it. SO research, research, research...www.cisco.com will have everything you need to find out about your equipment.