Mapping a MAC to an IP...

Todd Snyder tsnyder at
Wed Jan 21 16:17:55 UTC 2009

The spot we ran in to this problem the most is on a provisioning network
- there can be 1 or 200 servers being provisioned, and we found it
simplest at times to just make host declarations, but we want the range
for any NEW servers that come in.  Because it's during provisioning
stuff, we don't want the IP to change, so we ended up assigning the
first IP they were given by DHCP as their static IP.  not a great
system, but not something we wanted to fight with, and it just kept
growing and growing and growing, as hack jobs tend to do :)

I will have to give the reservation a shot - thanks!!



-----Original Message-----
From: dhcp-users-bounces at
[mailto:dhcp-users-bounces at] On Behalf Of Simon Hobson
Sent: Wednesday, January 21, 2009 11:00 AM
To: Users of ISC DHCP
Subject: RE: Mapping a MAC to an IP...

At 10:51 -0500 21/1/09, Todd Snyder wrote:
>My understanding is that you have to "break" the range to add host 
>This, to me, is the biggest pain I have with DHCP in a a production 
>environment.  What could be a nice general range declaration, with some

>hosts entries turns into a bunch of broken up and hard to dissect range

>declarations with hosts declarations sprinkled throughout.  for 5 
>entries, it's no biggie, but when putting in 50 or 60 hosts into a /24 
>there are a lot of lines. Multiply that by a few /24's and maintenance 
>gets to be quite difficult at times.

I've never had a problem that way, but then I'm managed my IP's rather
than scattering stuff all over the subnet in a random manner ! 
I guess that's no help if you've inherited a network from an admin that
just plugged stuff in and let it keep the address it got :-(

Also, if you are in that situation, there is now (I believe) another
option - you can mark a lease as reserved and it will be handled the
same as a dynamic address EXCEPT that it will be kept for use by the
same client and never re-allocated.

Simon Hobson

Visit for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.
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