Move dhcp lease to new ip+reservation. How?
Glenn Satchell
glenn.satchell at uniq.com.au
Fri Aug 27 04:54:36 UTC 2021
Hi Greg,
What about using a class for the 51-70 pool and use sub-classes to
define the allowed mac addresses? There's an example in the dhcpd.conf
man page, a bit like this. The leading 1 is added to the mac address to
indicate hardware type 1 (ethernet).
class "allocation-class-2" {
match pick-first-value (option dhcp-client-identifier, hardware);
}
subclass "allocation-class-1" 1:8:0:2b:4c:39:ad;
subclass "allocation-class-2" 1:8:0:2b:a9:cc:e3;
subclass "allocation-class-1" 1:0:0:c4:aa:29:44;
regards,
Glenn
On 2021-08-27 13:37, Gregory Sloop wrote:
> I have a subnet in dhcpd - lets just assume 192.168.1.0/24
>
> (It's a fail-over served pool - if that matters.)
>
> I have a pool where unknown-clients are allowed
>
> 192.168.1.21-40
>
> I'd like to add a new lease for a machine where the IP is outside the
> unknown pool above. (I don't want to use a host definition with an IP
> in the conf files, because I want the ddns name to get added via the
> DDNS mechanisms - which doesn't happen in that case. Plus, if this
> machine/device gets moved to another subnet, and the host def is still
> there, it won't get ANY lease in the new subnet - which is bad. I'd
> like the device to still function if it gets dropped into a new subnet,
> even if it's not getting a "special" ip any more.)
>
> This new machine/device may have already been added to the network and
> currently has an address in the 192.168.21-40 pool.
>
> Lets assume I'd like to assign it 192.168.1.51 - and set a reservation.
>
> Lets assume that I'll have several machines I'd like set as "static"
> between 51-70.
>
> But I don't want just "any" machine to get one of these "special"
> addresses in the 51-70 range.
>
> What's the best way to go about this?
>
> ---
>
> Some thoughts I've had, but this gets complicated.
>
> ---
>
> I don't believe I can just add or modify the lease without changing the
> pool, because even if there's a defined lease, this is still an unknown
> client. So, even if there's a reserved lease for 192.168.1.51 - the
> DHCP server won't give out that address because this is an unknown
> client. (Right?)
>
> Yet if I make a pool for 51-70 and allow unknown clients, then any
> client might (will) get one - not just the ones I want to "move" there.
>
> I've thought about pre-creating leases for 51-70 and essentially adding
> "bogus" information for those leases and reserving them. (While
> allowing unknown-clients for the 51-70 pool - but since they're all
> "taken" it won't hand one out), Then when I want to move something
> there, I can remove the "bogus" reservation and move the "real" lease
> to the appropriate IP in the 51-70 block/pool.
>
> ---
>
> Or define the MAC address in a host definition, without an IP
> definition. (I think DDNS works in this case.)
>
> Then define the 192.168.51-70 pool as "known" hosts only. (And make
> sure no "other" known hosts accidentally grab one of the IP's in this
> pool. This part worries me.)
>
> But it seems like I must be making this too hard.
>
> Am I missing something?
>
> Surely someone else has done this and can point me a tried-and-true
> solution that works without a ton of drama. :)
>
> (Yes, my pools are larger than those, but the details are essentially
> the same - this example is just more manageable.)
>
> Thanks!
>
> -Greg
>
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