DHCP "static" assignments

Brad Bendily Brad.Bendily at LA.GOV
Wed Aug 7 20:49:09 UTC 2013

So, we have subnets defined like this:
subnet netmask {
  range ;
  option routers ;

And If someone needs a static assignment, they are defined outside of the range/pool block.

host servername {
  hardware ethernet 00:50:56:55:55:55;

So, you could stack all of your host assignments in one section, or even in its own
config file.


-----Original Message-----
From: dhcp-users-bounces+brad.bendily=la.gov at lists.isc.org [mailto:dhcp-users-bounces+brad.bendily=la.gov at lists.isc.org] On Behalf Of Gregory Sloop
Sent: Wednesday, August 07, 2013 2:44 PM
To: Users of ISC DHCP
Subject: Re: DHCP "static" assignments

>>1) omshell/omapi unlimited reservation.
>>[Complicated, tl;dr - sounds like much hassle. :) ]

SH> Worth reading !
SH> Not much hassle, and these days I'd suggest it's the better way to 
SH> do it. The downside being that there isn't a trivially easy way to manage it.

Ok, perhaps I'll go back and try again - but management is pretty key, and conf files are more straight-forward, IMO.

>>e.g. pool 1-20, reserve 10
>>pool .. range 1-9 .. allow unknown-clients pool .. range 10 .. deny 
>>unknown-clients pool .. range 11-20 allow unknown-clients

SH> The pool in the middle isn't needed - just leave it out altogether. 
SH> The only requirement is that the fixed address sin't in any dynamic range.

So, if there's no pool, but a defined host, the DHCP server will hand out that IP for any host with the matching MAC address? Really!??!

I was under the impression there had to be a pool for the DHCP server to hand addresses out of...and that the "deny unknown-clients" just made sure it didn't hand out IP's in that pool to hosts not already defined.

[IMO, it would still be a lot easier if you just had to put in the host entry, and then define the pool as 1-20, and it wouldn't assign any IP's for defined hosts to any other host.

But, I know it just doesn't work that way, and probably for some good reasons I haven't considered...but as long as I'm wishing! :) ]

SH> As to whether you need to "deny unknown clients", I'm not sure. I 
SH> vaguely recall seeing postings to the effect that a client will 
SH> continue using it's dynamic address after you've created a fixed 
SH> address reservation for it - but I've not got that in my home setup 
SH> and that works fine. I don't recall having to do it in the past 
SH> either, back when I used dhcp a bit more "in anger" as it were.

SH> There is another method, but that tends to be used more when you 
SH> need an assignment based on (for example) opetion 82. That involves 
SH> creating a class for each assignment, and a pool to go with it with 
SH> "allow members of ...".

I think I know what you're talking about, and it's not very applicable in the case I envision.


dhcp-users mailing list
dhcp-users at lists.isc.org

More information about the dhcp-users mailing list