[BBLISA] A question on DHCP "shoulds".

[Edward Ned Harvey]

> I know that I can tell a DHCP server that machine with MAC address
> [bla] is to always get IP address [foo] this seems straight forward
> but the question is, if machine with MAC address [bla] treats it's IP
> address as statically assigned, as in, it's hardwritten into the
> configuration/startup scripts, does that "violate" (for lack of a
> better term) the rules of DHCP?

Absolutely no problem.  I do this all the time, and here are the reasons
why:

If a linux machine is a dhcp client, then the linux machine will assign
itself whatever hostname the dhcp server says.  It will go modify its own
"hosts" file, and resolv.conf, and sysconfig/network.  I have a specific
requirement:  The "hosts" file must contain both the unqualified and FQDN of
the host.  "10.1.1.50  myserver  myserver.example.com"  But if the hsots
file is created by DHCP, that gets removed.  IMHO, I would call that OS
damage.  (A server should be totally static, and resilient, and behave well
regardless of other servers, within reasonable limits.)  Which means - sure,
that's no problem for laptops, but servers ... that's a big no-no.

So all linux servers get statically assigned IP's.

Now - I never want to accidentally assign some other server the same IP
address.  So obviously the static IP addresses are assigned *outside* of the
dynamic pool.  But just to be really really sure ... I create  DHCP
reservation for each server, which will never be used because the server
will never request dhcp.

By creating the reservation, I ensure it can never be assigned, even by
accident, to any other system.