Logging DHCP lease duration in seconds

[Bob Harold]

>
>
> On Sun, Oct 4, 2015 at 3:47 PM, Glenn Satchell <glenn.satchell at uniq.com.au
> > wrote:
>
>> Hi Alp
>>
>> lease-time shows the remaining time in the lease, not the total time.
>>
>> This is from the dhcp-eval man page:
>>
>>      lease-time
>>
>>        The duration of the current lease - that is,  the  differ-
>>        ence  between the current time and the time that the lease
>>        expires.
>>
>> regards,
>> -glenn
>>
>> On Sat, October 3, 2015 6:51 am, Denis Laventure wrote:
>> > The client will renew the lease at half the max-lease-time. So seeing
>> 150
>> > sec for a 300 sec lease seems normal.
>> >
>> > Hi,
>> >
>> > I have an easy question I believe, I want to log DHCP lease durations
>> > given to clients, I tried the following, however it appears most of the
>> > time, logs are showing half of the lease duration.
>> >
>> > log(info, concat( "IP: ", binary-to-ascii(10, 8, ".", leased-address),
>> " ;
>> > ", "leasetime:", binary-to-ascii(10,32,"",encode-int(lease-time,32)) ));
>> >
>> > I have set the following lease time values for a pool:
>> >
>> > subnet 172.16.2.0 netmask 255.255.255.0 {
>> >   option routers 172.16.2.1;
>> >   pool {
>> >     failover peer "failover-partner";
>> >     default-lease-time 300;
>> >     min-lease-time 300;
>> >     max-lease-time 300;
>> >     range
>> 172.16
>> https://www.dibbssm.net/GroupFiles/Group167/Documents/Cubs/E1_Cub_Fun_In_the_Snow.pdf.2.10
>> 172.16.2.250;
>> >   }
>> > }
>> >
>> > And this configuration produces an output like this:
>> >
>> > Oct  2 14:34:44 mercan dhcpd: IP: 172.16.2.127 ; leasetime:155
>> > Oct  2 14:37:10 mercan dhcpd: IP: 172.16.2.127 ; leasetime:154
>> > Oct  2 14:37:13 mercan dhcpd: IP: 172.16.2.127 ; leasetime:297
>> > Oct  2 14:39:37 mercan dhcpd: IP: 172.16.2.127 ; leasetime:156
>> > Oct  2 14:42:03 mercan dhcpd: IP: 172.16.2.127 ; leasetime:154
>> > Oct  2 14:44:28 mercan dhcpd: IP: 172.16.2.127 ; leasetime:155
>> > Oct  2 14:46:53 mercan dhcpd: IP: 172.16.2.127 ; leasetime:155
>> > Oct  2 14:49:18 mercan dhcpd: IP: 172.16.2.127 ; leasetime:155
>> > Oct  2 14:49:54 mercan dhcpd: IP: 172.16.2.127 ; leasetime:264
>> > Oct  2 14:50:47 mercan dhcpd: IP: 172.16.2.127 ; leasetime:247
>> > Oct  2 14:51:18 mercan dhcpd: IP: 172.16.2.127 ; leasetime:269
>> >
>> > How can log the precise lease durations, would be great if anyone has
>> any
>> > suggestions?
>> >
>> > Thanks in advance.
>> > Alp
>>
>
Reading the man pages, try replacing:
     lease-time
with:
      config-option dhcp-lease-time

But do some packet traces to be sure that it truly gives the lease time in
the first ack packet, which might be the mclt instead of the normal lease
time if failover is used.

I would like to try it myself sometime when I get a chance.

-- 
Bob Harold
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.isc.org/pipermail/dhcp-users/attachments/20151005/ad759975/attachment.html>