what are the benefits of dhcp in a LAN?

[Harry Kuhman]

I see a lot of people, using dhcp for their lan, and don't understand the benefits.

With DHCP, IP addresses are assigned automagically. Without DHCP you have to assign an unique IP address in your subnet to every computer in your system.

While it might not be that big of a deal to set up a static IP address on a ciouple of computers in a home system, if you are testing other equipment DHCP takes care of this for you. If someone comes over with a notebook and you plug them into your system, DHCP assigns them a unique IP address on your network, even if the IP address they had on their home system is already in use by another of your computers (very handy for a lan party when several people come over). And, of most relavence to a Knoppix forum; if you boot Knoppix from CD and have DHCP available, you will be on the network as soon as you boot, with no set-up needed at all (assuming the boot version of Knoppix has support for your NIC and some evil company that hates Linux hasn't played games with your NIC's EEPROM in a "security update:, but that's another story).

I'm used to static IPs.
My example is: I have a /etc/host:
192.168.4.2 desktop
192.168.4.3 laptop

To make a filetransfer, I start

ftpd

on the desktop, and

ftp desktop

on the laptop.

When I use dhcp, will the laptop find the desktop too?

That's not DHCP exactly, that's Name Resolution. How it works in Linux I'm not sure. Yes, it works that way in Windows just fine, I can talk to my VPN server by telling the VPN client that I want to connect to 192.168.2.100 or that I want to connect to "AMD". I can ping by IP address or by name. And so on. Name resolution should work in a system independent of using DHCP or static addresses (in fact, there is no reason why you can't have a network with some static addresses and some dynamic ones. There are actually some good reasons for doing this if your DHCP server doesn't allow you to permanently lock some computers to dedicated addresses).

I need a hardware-router for this - or an additional service running permanently in the background, don't I?

Well, for DHCP, something has to be a DHCP server. If you have a high speed connection, I personally wouldn't consider runnng it without a router. (Please note: I'm talking about even a mininal $10 home DSL/cable router, not some expensive piece of Cisco equipment.) And certainly this is even more true if you have multiple computers on the network. In fact I'm wondering how you think it is that you are running a network with two computers on the private 192.168.xxx.xxx subnet without a router to provide NAT services (unless that's a completely independent network from the one you access the Internet with). But while a DHCP server needs to be somewhere, there is at least one simple case where you can and do use DHCP without having a router or other hardware or an additional service running in the background: Most high speed cable users connect to their provider and get their IP address from the cable company's DHCP server. So if you are on cable you can usually boot and have Knoppix come right up on the Internet on a computer connected directly to the cable modem (this is not true for cable companies who assign each user a sttatic IP address that they have to configure into their software before connecting, not is it true for DSL users without a router who must run PPPoE to connect to their modem). I certainly don't recommend connecting to the Internet this way, as a router provides an extra and important lever of firewall security as well, but it can and is frequently done.