DHCPv6 renew timer problem

Vladimir-M. Obelic vobelic at gbit6.net
Mon May 14 19:12:22 UTC 2012

On Fri, May 11, 2012 at 9:16 PM, Vladimir-M. Obelic <vobelic at gbit6.net> wrote:
> On Thu, May 10, 2012 at 11:30 PM, Vladimir-M. Obelic <vobelic at gbit6.net> wrote:
>> Hi,
>> I'm using the 4.1.1.-P1 version of dhcp server in IPv6 mode.
>> I'm having a problem regarding the renew timer.
>> A client (non isc, part of the SpirentTestCenter app/tool) solicits a
>> lease with explicitly defined renew timer. The ISC server replies with
>> both T1 and T2 set to 0.
>> On the client itself no renewal operation is performed and the lease
>> expires when the lease time expires.
>> The only extra options (except subnet6/range6) that I used in
>> dhcpd.conf is 'default-lease-time 6000; max-lease-time 7200;'.
>> Here's the wireshark capture of the 4-way dhcpv6 session:
>> http://pastebin.com/3j5wznRZ
>> As you can see the client solicits with T1/T2 values set explicitly.
>> The server apparently ignores this.
>> A different server, the STC dhcpv6 server explicitly sends the T2/T1
>> values in the advertise/reply messages and the client properly renews
>> the lease. I'm guessing the client must be told the T2/T1 timer
>> values, else it assumes renew/rebind is disabled?
>> Basically is there a way to force the server to supply T2/T1 timer values?
>> Any suggestions?
>> Thanks in advance
>> Regards,
>> Vladimir
> Well apparently 'option dhcp-rebinding-time' and 'option
> dhcp-renewal-time' can in fact be configured even though it's stated
> they aren't "user configurable", w/e that means.
> While browsing through the code in dhcpv6.c, I came upon this comment
> "T1/T2 time selection is kind of weird.  We actually use DHCP (v4)
> scoped options as handy existing places where these might be
> configured by an administrator".
> Does that mean T1/T2 time selection isn't implemented at all on the
> server side (save for the earlier mentioned options)?
> I have never seen the server to supply any other T1/T2 value that
> isn't 0. Not even when the client was dhclient -6.
> Any thought on this?
> Vladimir

Turns out I was following outdated man pages and documentation so that
was the root of all confusion..
Sorry guys.


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