[Dnsmasq-discuss] Lease comes back after removing

[Geert Stappers]

On Sun, Jun 23, 2019 at 09:33:21AM -0700, A C wrote:
> On 2019-06-23 03:32, Geert Stappers wrote:
> > On 23-06-2019 08:06, A C wrote:
> > 
> >> I'm having trouble removing leases from my system.  I have a client that
> >> accepted a lease in my DHCP range before I remembered to put it in
> >> /etc/ethers and /etc/hosts to give it a static lease.
> >>
> >> I turned off the client, stopped dnsmasq, removed the lease file entry
> >> in /var/lib/misc/dnsmasq.leases and then restarted dnsmasq.  Then I
> >> restarted the client.  It again found the original lease in my DHCP
> >> range instead of picking one from /etc/ethers (in fact it reports "not
> >> giving name ap.lan to the DHCP lease of 10.0.200.102 because the name
> >> exists in /etc/hosts with address 10.0.0.252").

Please check if I understand that,
that the configuration is simular to this:

/etc/dnsmasq.conf:

dchp-range=10.0.200.101-10.0.200.150    
readethers


/etc/ethers
00:00:ca:fe:be:ef   ap.lan


/etc/hosts

10.0.0.252  ap.lan



> >> How can I fully purge the lease and get it to start over?  The client is
> >> an embedded device and has no memory of the lease once I power cycle it
> >> so somehow dnsmasq is remembering even though the lease file was purged.
> >>
> > Recently I had simular sympthoms, infact still have them.
> > 
> > It give me the akward feeling that `readethers` does not work as I expect.
> > 
> > Because it was the first time that i used Dnsmasq with  /etc/ethers I
> > choose to continue with the netboots I have to do.
> > 
> > 
> > Yes, most likely will it bite me another time.
> > 
> > Meanwhile send your report of (successfull) mapping of IPv4 address on
> > MAC address through  /etc/ethers
> 
> /etc/ethers works fine for me, I have 50 clients listed in it, no issues. 

Acknowledge on that.  ( and no questions asked why it works fine )


> My only issue is when I forget to add a client to the list
> prior to first putting it online and it acquires a lease from the DHCP
> lease pool instead of the IP I want to give it via the combination of
> ethers/hosts.  After that I have extreme difficulty purging the lease to
> force a new address.


My /etc/ethers has a line like

00:02:b0:ef:f0:ef  kornuit

Doing `host kornuit` returns correctly the IPv4 address that is in DNS.
(other DNS as dnsmasq  ( no kornuit entry in /etc/hosts ))


I also stopped dnsmasq, removed the lease file and restarted dnsmasq.

Did another PXE netboot  ( consider it an embedded device, it has no
memory of previous lease )

Server kornuit got the IPv4 address as before, one from the Dnsmasq
DHCP range. Where it looks like a persistent DHCP lease, do I think
that it is algoritme that hands out each time the same IPv4 address.

Thing I need to verify is if dnsmasq does do a DNS-lookup on 'kornuit'
after reading /etc/ethers.


Groeten
Geert Stappers
-- 
Leven en laten leven