dhcpinform or dhcprequest
Tom Schmitt
TomSchmitt at gmx.de
Wed Sep 2 15:22:54 UTC 2009
-------- Original-Nachricht --------
> Datum: Wed, 2 Sep 2009 13:39:44 +0100
> Von: Simon Hobson <dhcp1 at thehobsons.co.uk>
> An: Users of ISC DHCP <dhcp-users at lists.isc.org>
> Betreff: Re: dhcpinform or dhcprequest
> >Now to the question:
> >In my understanding the client should at some point before the
> >leasetime is ended (normally at half the leasetime) send a
> >DHCPREQUEST to renew its lease. Then the DHCP server would send a
> >DHCPACK with a longer leastime.
>
> Correct
>
> >But what I see in the logfile of the DHCP server is something else:
> >At half of the leasetime the client is sending a DHCPINFORM instead
> >of a DHCPREQUEST.
> >The DHCP server is answering with a DHCPACK but the leasetime stay
> >the same, the lease is not renewed.
>
> DHCP Inform is not for lease renewal - it is separate and is designed
> to allow applications to query the server for options. Internet
> Explorer is a well known example of this, it will do a DHCP Inform to
> find out if it should be using a proxy (amongst other stuff).
>
> >A few minutes later the leasetime is ended and the DHCP server sends
> >an update to the DNS, deleting the entry of the client.
> >But the client still uses this IP, only now having trouble because
> >of the missing DNS entry.
> >
> >My question:
> >Is this really a problem on clientside? (If yes, know anyone a
> >solution for this?)
>
> Yes, it's a broken client - very broken.
>
> Hard to see how much more broken it could be.
> - Attempts to renew using DHCP Inform
> - Fails to renew
> - Continues using address
>
> Solution, ditch the client ! Of course, if the vendor can fix it then
> demand that they do.
Thank you for the good explanation. This is very helpfull.
Sadly I have not much hope that the vendor will change anything: The Client is a HP workstation with Windows XP and Microsoft is not well known for changing their software based on a request from a single person.
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