Re: dhcpd(8) and unused or old MAC addresses

[rockyhotas%firemail.cc@localhost]

On 2023-08-22 15:41, Greg Troxel wrote:
> This works and I do it all the time.
>
> Edit the file and delete the specific lease.  Then restart dhcpd.
> However, I am unclear on when it writes the lease file and if it reads
> it other than at startup.   I think it reads it on startup, and then 
> the
> working copy in RAM is what counts and it writes it when it issues a
> lease.   So if you write/restart without a lease renewal, this works.
>
> Best practice is surely to stop the daemon, edit, and restart.

Ok, good, thank you!

> But basically you shouldn't care, unless you want your IP address space
> tidy.  If that's what you want, then you probably should configure your
> dhcpd:
[...]
>   statically assign (NOT in the pool!) in dhcpcd addresses to specific
>   devices based on IP address or client-id (you can steal these lines
>   from the lease file) organized in some way that makes senes to you,
>   like a block of 8 or 10 for one persons phone-type devices, a block
>   for accees points, etc.
[...]
> The basic expression is
>
>   host foo {
>     hardware ethernet bar;
>     fixed-address 192.168.100.11;
>   }

I am not sure that I understood what you are meaning. Are you suggesting
to explicitly specify in /etc/dhcpd.conf some entries for some selected
devices, so that - if they make a dhcp request - they always get the 
same
IP, fully controlled by me?

> After you edit and restart, make sure it's running because it will fail
> to start on syntax error and you will notice hours later when devices
> can't get leases.

This also is a very useful advice.

Thanks!

Rocky