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David Brook wrote:
> Can someone please tell me how DNS and DHCP interact?
>
> I understand the concept of DNS and DHCP as individual entities,
> however, I cannot see how they can both operate on the same
network -
> how can the DNS resolve dynamically allocated IP addressing?
DNS is now dynamic (well some implementations - ISC and Microsoft).
Either the DHCP client (Microsoft W2K) or the DHCP server (ISC)
can notify the DNS server of a new lease, and so update the
forward and reverse mappings.
It is not so hard to understand. There is a little detail on
renewing registrations and the like which you don't want to
know, and building proper redundancy in is hard (assuming you
really want all your DNS updates promptly even when something
bad is happening).
I do it on my LAN, but mostly because I have done some big DNS
designs, and like to keep my hand in with esoteric stuff.
First ask a few questions;
Do you want static IP addresses? Typically servers want to stay
on the same IP address, and DNS servers MUST have the same IP
address.
But client machines don't normally matter, you don't usually
offer services from machines being rebooted all the time! Indeed
client to client networking is usually a recipe for disaster in
Office networks. So the client machines could have no, or dummy
entries in the DNS - like DHCP{01|02|03|04}.
You can also use DHCP to manage static IP addresses, hand out
the same address to the same client each time, but allows you to
update other DHCP information quickly (default route, DNS
servers, domains), and renumber from a central location. But I
think for server machines you probably want them to boot and
work even when bits of the network are having a glitch.
DHCP in particular is a bit of a pain to make properly
redundant. Although the ISC product does have a mechanism for
DHCP server redundancy, it sucks, and the Microsoft solution
wasn't any better last time I looked. Microsoft's advice, locate
DHCP server on highly redundant hardware <doh>.
ISC Dynamic DNS doesn't have decent redundancy mechanisms built
in, if the master is down for too long, upgrade a slave.
One other solution is dnsmasq, which combined simple DNS with
access to the DHCP lease file. Looked okay for small networks, I
have a note that I should audit the code before I recommend it.
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