I want to study DNS and DHCP. Do I need a router?

[asker2013]

Hi everyone. I am new to this forum and this is my first post.

I have three laptops, three 2-meter straight-through cables, and a D-Link 8-port 10/100 Desktop switch (DES-1008A).
I want to study DNS and DHCP in Ubuntu by creating a small INTERNAL network (1 server and 2 clients).
I have installed Ubuntu 12.04 desktop i386 32bit in all three laptops and have downloaded and updated all necessary files for my study.

My questions are:

1. Do I need to buy a router? If so, what is the exact model of the cheapest router that will suffice for my needs?

2. If I don't need a physical router, how will I configure my default gateway?

Thanks in advance!

[SeijiSensei]

If the server allows you to install a second network card, you can configure it to be a NAT router.

Alternatively you can just buy a basic router for $25-30 from some place like NewEgg. Read the reviews.

[Iowan]

I have a separate Ubuntu box set up as DHCP/DNS server. I disabled the DNS/DHCP server in my router.
( I also bought a used DLink WRT-54GL with Tomato ... although I haven't put it online, yet.)

My first router was a floppy-based Freesco dial-up machine.