DHCP lease expiration and address renewal

[Margaret Ringia Hart]

An associate of mine (who allegedly has MCSE certification) tells me that in
a DHCP environment, the clients' IP addresses only renew (pick a different
address from the available DHCP pool) if they get turned off - and stay
powered off - for a period of time = to the the length of the lease (or 1/2
the length of the lease in some cases). In this case - if the lease term was
7 days and the the lease was set to expire in 1 day (as indicated by
IPCONFIG), that PC would not get a new address the next day when it logged
in -- since it would have only been powered off overnight.

Somehow -- this just doesn't seem right to me.

My understanding is: when a DHCP client PC's IP address lease expires - so
too does that PC's IP address, and the client PC will be assigned a new and
different IP address the next time it is rebooted or logs in again --
REGARDLESS OF HOW LONG THE PC WAS OFF LINE/LOGGED OUT/POWERED OFF.

Which is correct?

Thanks in advance.

SH

 

[Richard G. Harper]

From the source:

http://support.microsoft.com/Default.aspx?kbid=169289

--
Richard G. Harper [MVP Shell/User] (e-mail address removed)
* PLEASE post all messages and replies in the newsgroups
* for the benefit of all. Private mail is usually not replied to.
* My website, such as it is ... http://rgharper.mvps.org/
* HELP us help YOU ... http://www.dts-l.org/goodpost.htm

 

[Phillip Windell]

Neither really.

1. A client will always try to renew the lease at the 50% point (4 days with
an 8 day lease).

2. A client will aways ask for the same number it had last time no matter
what.

3. If a client is turned off for a period of time it will make no difference
unless another device was given that IP# while the first client was turned
off. This does not happen often since every other device will also ask for
the same IP# it had last time so they won't be "stealing" each other's IP#s.
However a "new" device entered into the sytem might do so.

4. So regaurdless,...a client will always ask the same DHCP machine for the
same IP# it had last time. It the IP# is available it will get it,...if not
it will get a new one.

Richard's article should probably verify that (I haven't seen it),...but if
not he can spank me later ;-)


--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com
-----------------------------------------------------
Understanding the ISA 2004 Access Rule Processing
http://www.isaserver.org/articles/ISA2004_AccessRules.html

Troubleshooting Client Authentication on Access Rules in ISA Server 2004
http://download.microsoft.com/download/9/1/8/918ed2d3-71d0-40ed-8e6d-fd6eeb6cfa07/ts_rules.doc

Microsoft Internet Security & Acceleration Server: Guidance
http://www.microsoft.com/isaserver/techinfo/Guidance/2004.asp
http://www.microsoft.com/isaserver/techinfo/Guidance/2000.asp

Microsoft Internet Security & Acceleration Server: Partners
http://www.microsoft.com/isaserver/partners/default.asp

Deployment Guidelines for ISA Server 2004 Enterprise Edition
http://www.microsoft.com/technet/prodtechnol/isa/2004/deploy/dgisaserver.mspx

 

[Richard G. Harper]

That was nothing but net from here.

(Gee, not only a pun but given that the NCAA and NIT tournaments are just
around the corner, a well-timed one at that. Mebbe I am talented after all.
<G>)

--
Richard G. Harper [MVP Shell/User] (e-mail address removed)
* PLEASE post all messages and replies in the newsgroups
* for the benefit of all. Private mail is usually not replied to.
* My website, such as it is ... http://rgharper.mvps.org/
* HELP us help YOU ... http://www.dts-l.org/goodpost.htm

Neither really.

1. A client will always try to renew the lease at the 50% point (4 days
with
an 8 day lease).

2. A client will aways ask for the same number it had last time no matter
what.

3. If a client is turned off for a period of time it will make no
difference
unless another device was given that IP# while the first client was turned
off. This does not happen often since every other device will also ask for
the same IP# it had last time so they won't be "stealing" each other's
IP#s.
However a "new" device entered into the sytem might do so.

4. So regaurdless,...a client will always ask the same DHCP machine for
the
same IP# it had last time. It the IP# is available it will get it,...if
not
it will get a new one.

Richard's article should probably verify that (I haven't seen it),...but
if
not he can spank me later ;-)


--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com
-----------------------------------------------------
Understanding the ISA 2004 Access Rule Processing
http://www.isaserver.org/articles/ISA2004_AccessRules.html

Troubleshooting Client Authentication on Access Rules in ISA Server 2004
http://download.microsoft.com/download/9/1/8/918ed2d3-71d0-40ed-8e6d-fd6eeb6cfa07/ts_rules.doc

Microsoft Internet Security & Acceleration Server: Guidance
http://www.microsoft.com/isaserver/techinfo/Guidance/2004.asp
http://www.microsoft.com/isaserver/techinfo/Guidance/2000.asp

Microsoft Internet Security & Acceleration Server: Partners
http://www.microsoft.com/isaserver/partners/default.asp

Deployment Guidelines for ISA Server 2004 Enterprise Edition
http://www.microsoft.com/technet/prodtechnol/isa/2004/deploy/dgisaserver.mspx
-----------------------------------------------------

An associate of mine (who allegedly has MCSE certification) tells me that in
a DHCP environment, the clients' IP addresses only renew (pick a
different
address from the available DHCP pool) if they get turned off - and stay
powered off - for a period of time = to the the length of the lease (or 1/2
the length of the lease in some cases). In this case - if the lease term was
7 days and the the lease was set to expire in 1 day (as indicated by
IPCONFIG), that PC would not get a new address the next day when it
logged
in -- since it would have only been powered off overnight.

Somehow -- this just doesn't seem right to me.

My understanding is: when a DHCP client PC's IP address lease expires -
so
too does that PC's IP address, and the client PC will be assigned a new and
different IP address the next time it is rebooted or logs in again --
REGARDLESS OF HOW LONG THE PC WAS OFF LINE/LOGGED OUT/POWERED OFF.

Which is correct?

Thanks in advance.

SH

 

[Margaret Ringia Hart]

Very well done guys. Thanks for the clarification!

 

[Phillip Windell]

Hey Richard.
There is another MVP Event in Chicago on April 21st. I don't know anything
about it but it sounds like the same type of thing as last year.
I haven't decided on it or signed up yet, but thought I'd mention it.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

That was nothing but net from here.

(Gee, not only a pun but given that the NCAA and NIT tournaments are just
around the corner, a well-timed one at that. Mebbe I am talented after all.
<G>)

--
Richard G. Harper [MVP Shell/User] (e-mail address removed)
* PLEASE post all messages and replies in the newsgroups
* for the benefit of all. Private mail is usually not replied to.
* My website, such as it is ... http://rgharper.mvps.org/
* HELP us help YOU ... http://www.dts-l.org/goodpost.htm

Neither really.

1. A client will always try to renew the lease at the 50% point (4 days
with
an 8 day lease).

2. A client will aways ask for the same number it had last time no matter
what.

3. If a client is turned off for a period of time it will make no
difference
unless another device was given that IP# while the first client was turned
off. This does not happen often since every other device will also ask for
the same IP# it had last time so they won't be "stealing" each other's
IP#s.
However a "new" device entered into the sytem might do so.

4. So regaurdless,...a client will always ask the same DHCP machine for
the
same IP# it had last time. It the IP# is available it will get it,...if
not
it will get a new one.

Richard's article should probably verify that (I haven't seen it),...but
if
not he can spank me later ;-)


--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com
-----------------------------------------------------
Understanding the ISA 2004 Access Rule Processing
http://www.isaserver.org/articles/ISA2004_AccessRules.html

Troubleshooting Client Authentication on Access Rules in ISA Server 2004
http://download.microsoft.com/download/9/1/8/918ed2d3-71d0-40ed-8e6d-fd6eeb6cfa07/ts_rules.doc

Microsoft Internet Security & Acceleration Server: Guidance
http://www.microsoft.com/isaserver/techinfo/Guidance/2004.asp
http://www.microsoft.com/isaserver/techinfo/Guidance/2000.asp

Microsoft Internet Security & Acceleration Server: Partners
http://www.microsoft.com/isaserver/partners/default.asp

Deployment Guidelines for ISA Server 2004 Enterprise Edition
http://www.microsoft.com/technet/prodtechnol/isa/2004/deploy/dgisaserver.mspx
-----------------------------------------------------

An associate of mine (who allegedly has MCSE certification) tells me

that
in

a DHCP environment, the clients' IP addresses only renew (pick a
different
address from the available DHCP pool) if they get turned off - and stay
powered off - for a period of time = to the the length of the lease (or 1/2
the length of the lease in some cases). In this case - if the lease

term
was

7 days and the the lease was set to expire in 1 day (as indicated by
IPCONFIG), that PC would not get a new address the next day when it
logged
in -- since it would have only been powered off overnight.

Somehow -- this just doesn't seem right to me.

My understanding is: when a DHCP client PC's IP address lease expires -
so
too does that PC's IP address, and the client PC will be assigned a new and
different IP address the next time it is rebooted or logs in again --
REGARDLESS OF HOW LONG THE PC WAS OFF LINE/LOGGED OUT/POWERED OFF.

Which is correct?

Thanks in advance.

SH

 

[Richard G. Harper]

Sadly, I've had some post-op problems with the bad arm (that you saw in a
sling the last time we met) - nothing serious but just enough to put me on
the no-fly list for a while. The wife and I were discussing making a long
weekend of it like we did last year.

<sigh>

--
Richard G. Harper [MVP Shell/User] (e-mail address removed)
* PLEASE post all messages and replies in the newsgroups
* for the benefit of all. Private mail is usually not replied to.
* My website, such as it is ... http://rgharper.mvps.org/
* HELP us help YOU ... http://www.dts-l.org/goodpost.htm

 

[Phillip Windell]

Sadly, I've had some post-op problems with the bad arm (that you saw in a
sling the last time we met) - nothing serious but just enough to put me on
the no-fly list for a while.

Tell them you promise not to stick your arm out the window during fight.

The wife and I were discussing making a long
weekend of it like we did last year.

That wouldn't be so bad. If I wasn't always broke I'd spend a little extra
time up there checking things out, but the hotels cost would kill me. I
just drive up there,..I'm about 4 hours south. I haven't signed up yet, but
I probably will in a few days.

 

[Guest]

It will attempt to renew the IP it had before the expiration. If that IP is
no longer available it will get the next available one. It is true though
that it will attempt to renew the lease at 50%.