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Re: strange DHCP behaviour




On 23/10/2018 21:03, mick crane wrote:
> On 2018-10-23 14:56, Tony van der Hoff wrote:
>> Hi, I havea laptop running fully up to date Stretch with NetworkManager,
>> set to use DH|Cp via wireless.
>>
>> The DHCP server is another Stretch system, with the stanzas
>> host tony-lt {
>>     hardware ethernet 0c:60:76:6c:e6:6f;
>>     fixed-address 192.168.1.199;
>>     }
>> subnet 192.168.1.0 netmask 255.255.255.0
>>     {
>>         range 192.168.1.200 192.168.1.254;
>>         option routers 192.168.1.10;
>>     }
>>
>> That MAC is correct for the laptop.
>>
>> I an expecting to see 192.168.1.199 as the laptop address, but no, if a
>> gives:
>> wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP
>> group default qlen 1000
>>     link/ether 0c:60:76:6c:e6:6f brd ff:ff:ff:ff:ff:ff
>>     inet 192.168.1.253/24 brd 192.168.1.255 scope global dynamic wlan0
>>        valid_lft 479sec preferred_lft 479sec
>>
>> Finally, the server shows:
>> Oct 23 14:23:38 routerpi dhcpd[1068]: DHCPREQUEST for 192.168.1.253 from
>> 0c:60:76:6c:e6:6f (tony-lt) via eth0
>> Oct 23 14:23:38 routerpi dhcpd[1068]: DHCPACK on 192.168.1.253 to
>> 0c:60:76:6c:e6:6f (tony-lt) via eth0
>> Oct 23 14:23:53 routerpi dhcpd[1068]: reuse_lease: lease age 15 (secs)
>> under 25% threshold, reply with unaltered, existing lease for
>> 192.168.1.253
>> Oct 23 14:23:53 routerpi dhcpd[1068]: DHCPREQUEST for 192.168.1.253 from
>> 0c:60:76:6c:e6:6f (tony-lt) via eth0
>> Oct 23 14:23:53 routerpi dhcpd[1068]: DHCPACK on 192.168.1.253 to
>> 0c:60:76:6c:e6:6f (tony-lt) via eth0
>>
>> So, my question: why is the server handing out .253, when it is
>> configured to provide .199?
>> What is this 'reuse-lease' all about?
>>
>> I've tried 'dhclient -r wlan 0; dhclient -v wlan0' on the laptop, to no
>> avail.
>>
>> Any suggestions, please?
> 
> bearing in mind that I've no idea what I'm talking about is it possible
> that the laptop connected to the server and got a really long lease on
> .253 before you added
> 
> host tony-lt {
> hardware ethernet 0c:60:76:6c:e6:6f;
>      fixed-address 192.168.1.199;
>      }
> probably there is a command to flush leases ?
> 
I've flushed the lease several times (The dhclient -r command mentioned
above does that), and physically deleted the lease files.  No good!

Cheers, Tony