Searching for documentation on dhcpT1value

Simon Hobson dhcp1 at thehobsons.co.uk
Sat Jan 10 09:37:50 UTC 2009


Halim Issa wrote:

>I'm running dhcpd 3.0.5 and have for a while now searched in vain for
>documentation on how dhcpT1value and dhcpT2value are to be set.
>
>The DHCP client makes the following complaint when being assigned an address:

Which client ?


>dhcpT1value is missing in DHCP server response. Assuming 3600 sec
>dhcpT2value is missing in DHCP server response. Assuming 6300 sec
>
>There is no mention of dhcpT.value in the man page, documentation directory or
>online, and a google search only shows up similar problems but no solutions,
>so I was hoping to find some enlightenment here.
>
>I tried adding dhcpT1value=3600 to my dhcpd.conf, but it only accepts values
>between 0 and 255, so my question is simple:
>
>1. What does dhcpT1value control that is different from default-lease-time and
>max-lease-time keywords?
>
>2. What unit is the value - seconds, minutes, ticks or what?
>
>3. What's the recommended use?

T1 and T2 are (IIRC) the times at which the client will firstly 
attempt to renew it's lease with the original issuing server, and if 
that fails, to broadcast for a new lease. The defaults are (IIRC) 1/2 
and 7/8ths of the lease time.

So the client will use it's lease for half the time given and then 
start asking the original server for a renewal (DHCP-Request 
message). It the original server fails to respond, then at 7/8ths of 
the lease time, the client will start to broadcast for a lease 
(DHCP-Discover message).

So with an 8 hour lease (and no DHCP servers running after issuing a 
lease), the client would do nothing for 4 hours, send DHCP-Request 
messages to the original server for 3 hours, broadcast DHCP-Discover 
messages for an hour, and finally unconfigure it's IP interfaces at 8 
hours when the lease runs out. Obviously, if a DHCP server responds, 
the timers reset and the client doesn't lose it's network connection.

 From 'man dhcp-options' :

>               o p t i o n   d h c p - r e b i n d i n g - t i m e  
> u i n t 3 2 ; 
> 
>                     T h i s   o p t i o n   s p e c i f i e s  
> t h e   n u m b e r   o f   s e c o n d s   f r o m   t h e  
> t i m e     a     c l i e n t     g e t s     a n    
> a d d r e s s     u n t i l     t h e     c l i e n t 
>                     t r a n s i t i o n s   t o   t h e  
> R E B I N D I N G   s t a t e . 
> 
>                     T h i s   o p t i o n   i s   n o t   u s e r  
> c o n f i g u r a b l e . 
> 
> 
>               o p t i o n   d h c p - r e n e w a l - t i m e  
> u i n t 3 2 ; 
> 
>                     T h i s   o p t i o n   s p e c i f i e s  
> t h e   n u m b e r   o f   s e c o n d s   f r o m   t h e  
> t i m e   a   c l i e n t   g e t s   a n   a d d r e s s  
> u n t i l   t h e   c l i e n t   t r a n s i  
>                     t i o n s   t o   t h e   R E N E W I N G   s t a t e . 
> 
>                     T h i s   o p t i o n   i s   n o t   u s e r  
> c o n f i g u r a b l e . 


-- 
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.



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