Configuring T1 & T2 Timers

Christopher Cain chris at
Tue Jul 19 22:25:05 UTC 2011

Thank you all for the responses. I personally don't think these values
should be altered either without good reason.  I'm just doing a bit of
research on behalf of a client.  Based on your responses (and what I was
able to Google), am I correct in assuming the ability to set these options
is only available in DHCP v4.2 and higher?

Christopher Cain
E: chris at

On Tue, Jul 19, 2011 at 17:25, <dhcp-users-request at> wrote:

> ---------- Forwarded message ----------
> From: Shawn Routhier <sar at>
> To: Users of ISC DHCP <dhcp-users at>
> Date: Tue, 19 Jul 2011 14:24:59 -0700
> Subject: Re: Configuring T1 & T2 Timers
> On 07/19/2011 13:29, Bruce Hudson wrote:
>> Hi all.  Is there a way to configure the T1 and T2 values in dhcpd.conf?
>>>>  If so, what is the syntax?
>>  I believe those timers are built into the client, and are not part of
>>> the DHCP lease. Therefore, I don't believe there is any way to configure
>>> it. I've certainly never seen anything like this in the man pages.
>>      From a fairly quick look at the code, the T1 and T2 timers can be set
>> in the server and passed to the client via options 58 and 59. Earlier
>> versions did not allow these to be set in the configuration. The server
>> calculated them from the offered lease. This appears to have changed in
>> (at least) the latest version; apparently for DCHPv6 support.
>>     The options specify a number of seconds not so using them seems risky
>> unless you set both min-lease-time and max-lease-time to the same value
>> and do your own calculations.
>> --
>> Bruce A. Hudson                         | Bruce.Hudson at Dal.CA
> See the descriptions for dhcp-renewal-time and dhcp-rebinding-time
> in common/dhcp-options.5.  These are user-configurable in 4.2.
> As Bruce mentions you will want to make sure they make sense with the
> lease time.
> Shawn
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