DHCPv6 renew timer problem

Vladimir-M. Obelic vobelic at gbit6.net
Fri May 11 19:16:30 UTC 2012

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?


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