Re: Move dhcp lease to new ip+reservation. How?

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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