[plug] Basic DHCP questions

[Colin Muller]

> My question is do I have to remove the hostname/ip addresses I have
> in the /etc/hosts file, and change the /etc/nsswitch.conf to be "dns
> file nis" instead of "files dns nis"?  How does dhcp or arp keep
> track of a machine hostname to ip address connection, when the ip
> addresses can change each time you reboot?  Is there a dhcp cache or
> config file maintained by dhcp which assigns hostnames to mac
> addresses to keep it all straight?

There are probably other and simpler ways, but I do this:

1. Run a domain name server on the DHCP server (192.168.1.1) which
  provides name-to-IP resolution for all machines on the LAN

2. In the relevant subnet section (in my case 192.168.1.0) of
  /etc/dhcpd.conf, put this line: 
  option domain-name-servers 192.168.1.1;

3. The group statement for the machines on the LAN goes like this:

group {
    use-host-decl-names on;
    host colinlabtop2 { 
	hardware ethernet 00:00:00:00:00:00;
	fixed-address colinlabtop2.homelan; 
    } 
    host joanibook { 
	hardware ethernet 00:000:00:00:00:00;
	fixed-address joanibook.homelan; 
    } 
    ... and so on, one host statement per machine on the LAN
 }

You replace the '00's in the ethernet lines with the real MAC numbers
of the ethernet cards on your LAN, which you can find when all
machines are connected by doing 'arp -a' on the server.

4. For good measure, make the hostnames of the machines on the LAN match
  the names in the host statements (here, colinlabtop2 and joanibook).

5. And for further good measure, I put into /etc/resolv.conf on each
LAN machine: nameserver 192.168.1.1

It's the colinlabtop2.homelan and joanibook.homelan addresses which
you need to have your DNS resolve to an IP; then DHCP will always give
them the same IP when a machine with the matching ethernet card
connects and ask for an IP. You won't need to change your /etc/hosts
if the IPs in it match those given by DNS.

['labtop' is an in-joke; it's not that I use the same spell-checker as
James and Tony :-)]

Colin