DHCP IP assigning for laptops

Hi everyone,

I have two subnets: A and B, and I have only one Win2003 DHCP server on
subnet A. With Relay Agent or I may say UDP Helper, normally DHCP server can
assign IPs to both subnets properly. Here's the problem: if some DHCP clients
moved to the other subnet, the moved DHCP clients would still persistently
request for its old IP(Option 50), then the Win2003 2003 DHCP server would
assign what IP the client had requested just because both DHCP pools for A
and B are in the same server and the same database. Thus the client with
wrong IP will fail to communcate with others.

As solutions, first, I don't want to BIND or use STATIC IP or use VLAN VMPS
because the clients like this are many; second, the router can only provide
Relay Agent function and nothing more at this point; third, the server must
be Windows Server 2003 Standard Edition.

I tried to use multihomed DHCP server design to solve this but in vain.
Because Windows 2003 DHCP server cannot bind server IPs separately, that
means no matter how many NICs you have, you can only bind them to ONE DHCP
database.

I'm exhausted and depressed. Any help here? I apprecate for any solution or
suggestion.

Hi,


The DHCP server will happily assigned the requested IP if it's available, by
design, and this behavior cannot be changed (unless reservation is in
effect). The problem is in the client requesting the IP it has already known,
which is not the desired result.

What you might want to try is setting the server/scope wide options to have
Windows 2000 or later DHCP clients to release IP upon shutdown. The next time
these computers request DHCP upon startup, they will have no known IP to
request, and the DHCP server will assign the IP addresses based on subnet
information, assuming the DHCP relay agent is configured properly.


I hope this will solve the problem. Please let me know if this works (or
will work) or I am wrong.


Dan

"Pagan" wrote:

> Hi everyone,
>
> I have two subnets: A and B, and I have only one Win2003 DHCP server on
> subnet A. With Relay Agent or I may say UDP Helper, normally DHCP server can
> assign IPs to both subnets properly. Here's the problem: if some DHCP clients
> moved to the other subnet, the moved DHCP clients would still persistently
> request for its old IP(Option 50), then the Win2003 2003 DHCP server would
> assign what IP the client had requested just because both DHCP pools for A
> and B are in the same server and the same database. Thus the client with
> wrong IP will fail to communcate with others.
>
> As solutions, first, I don't want to BIND or use STATIC IP or use VLAN VMPS
> because the clients like this are many; second, the router can only provide
> Relay Agent function and nothing more at this point; third, the server must
> be Windows Server 2003 Standard Edition.
>
> I tried to use multihomed DHCP server design to solve this but in vain.
> Because Windows 2003 DHCP server cannot bind server IPs separately, that
> means no matter how many NICs you have, you can only bind them to ONE DHCP
> database.
>
> I'm exhausted and depressed. Any help here? I apprecate for any solution or
> suggestion.

Hi,

First thank you for your help. Most of my DHCP clients are already WinXP
Pro. I had tried the way you said to work out: before shut down or restart,
release the DHCP IP, after booting the OS the option 50 of DHCP request would
be 0.0.0.0 instead of a old DHCP IP, the client therefore would be assigned
the desired IP from DHCP server. So the problem in reality is that I can't
possible tell or train every client to do so after they moved their laptop or
desktop to another physicial location of another subnet.

I've used some 3rd party DHCP server software in Win2003, strangely, it had
a founction that could ignore option 50 of DHCP request and assign a desired
IP to client and could even separate database of each NIC unlike Win2003 kept
only one database for all NIC. I just wonder why MS does not provide such
function or just I didn't find out?

Pagan

"Dan" wrote:

> Hi,
>
>
> The DHCP server will happily assigned the requested IP if it's available, by
> design, and this behavior cannot be changed (unless reservation is in
> effect). The problem is in the client requesting the IP it has already known,
> which is not the desired result.
>
> What you might want to try is setting the server/scope wide options to have
> Windows 2000 or later DHCP clients to release IP upon shutdown. The next time
> these computers request DHCP upon startup, they will have no known IP to
> request, and the DHCP server will assign the IP addresses based on subnet
> information, assuming the DHCP relay agent is configured properly.
>
>
> I hope this will solve the problem. Please let me know if this works (or
> will work) or I am wrong.
>
>
> Dan

Hi,

There is actually a Microsoft specific option inside DHCP server which you
can set to tell Windows 2000 or later DHCP clients to release their IP at
shutdown, in addition to the standard options like DNS server, gateway, WINS,
etc. That way, you don't have to worry about training your users to release
their computer's IP at shutdown.

"Pagan" wrote:

> Hi,
>
> First thank you for your help. Most of my DHCP clients are already WinXP
> Pro. I had tried the way you said to work out: before shut down or restart,
> release the DHCP IP, after booting the OS the option 50 of DHCP request would
> be 0.0.0.0 instead of a old DHCP IP, the client therefore would be assigned
> the desired IP from DHCP server. So the problem in reality is that I can't
> possible tell or train every client to do so after they moved their laptop or
> desktop to another physicial location of another subnet.
>
> I've used some 3rd party DHCP server software in Win2003, strangely, it had
> a founction that could ignore option 50 of DHCP request and assign a desired
> IP to client and could even separate database of each NIC unlike Win2003 kept
> only one database for all NIC. I just wonder why MS does not provide such
> function or just I didn't find out?
>
> Pagan
>
> "Dan" wrote:
>
> > Hi,
> >
> >
> > The DHCP server will happily assigned the requested IP if it's available, by
> > design, and this behavior cannot be changed (unless reservation is in
> > effect). The problem is in the client requesting the IP it has already known,
> > which is not the desired result.
> >
> > What you might want to try is setting the server/scope wide options to have
> > Windows 2000 or later DHCP clients to release IP upon shutdown. The next time
> > these computers request DHCP upon startup, they will have no known IP to
> > request, and the DHCP server will assign the IP addresses based on subnet
> > information, assuming the DHCP relay agent is configured properly.
> >
> >
> > I hope this will solve the problem. Please let me know if this works (or
> > will work) or I am wrong.
> >
> >
> > Dan
>

Hi,

Thanks, I never noticed that. But the problem now become more complicated,
first I must MANUALLY delete the IP addresses in address leases colum of the
DHCP server so that the DHCP server would not offer the CACHED old IP to the
client. Second, this method is only for the desktops which will shutdown by
moving to another subnet of another physical location, for laptop it might be
a bit annoying, I guess only VLAN VMPS will solve that. Third, what about the
minority Win98 and Win95 users?

So now the biggest problem is to prevent the cached undesired IP being
assigned to the DHCP client, or I may say to delete DHCP server cached IP
automatically.

Oh man, now I wonder if there are any 3rd party DHCP server software that
can solve all those trouble once for all and provide function of being
authorized to integrate with Active Directory.

"Dan" wrote:

> Hi,
>
> There is actually a Microsoft specific option inside DHCP server which you
> can set to tell Windows 2000 or later DHCP clients to release their IP at
> shutdown, in addition to the standard options like DNS server, gateway, WINS,
> etc. That way, you don't have to worry about training your users to release
> their computer's IP at shutdown.
>

"Pagan" <(E-Mail Removed).(nospam)> wrote in message
news:B629D334-A65D-4F48-BA67-(E-Mail Removed)...
> Thanks, I never noticed that. But the problem now become more complicated,
> first I must MANUALLY delete the IP addresses in address leases colum of
the
> DHCP server so that the DHCP server would not offer the CACHED old IP to
the
> client. Second, this method is only for the desktops which will shutdown
by
> moving to another subnet of another physical location, for laptop it might
be
> a bit annoying, I guess only VLAN VMPS will solve that. Third, what about
the
> minority Win98 and Win95 users?

VLANs probably won't solve anything, but then I don't have your earlier
posts so I may not have the full context..
This behavor is most commonly seen due to using a Superscope when you
shouldn't be using one.

We have multiple subnets and all kinds and types of machines and they all
adjust perfectly fine if moved to a new subnet.

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

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

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

Hi,

Thanks for you concern. The early posts are just above, well I see all this
via IE.

First, can you tell me how to let the clients automatically obtain desired
IP when they moved to another subnet? Does this revelent to superscope? I
tried to use or not to ues, same result.

Second, if the firewall can only recognize IP instead of MAC, how to grant
the clients permition to have Internet access? And these clients are laptop
which means they often move to another subnet.

Pagan

"Phillip Windell" wrote:

> "Pagan" <(E-Mail Removed).(nospam)> wrote in message
> news:B629D334-A65D-4F48-BA67-(E-Mail Removed)...
> > Thanks, I never noticed that. But the problem now become more complicated,
> > first I must MANUALLY delete the IP addresses in address leases colum of
> the
> > DHCP server so that the DHCP server would not offer the CACHED old IP to
> the
> > client. Second, this method is only for the desktops which will shutdown
> by
> > moving to another subnet of another physical location, for laptop it might
> be
> > a bit annoying, I guess only VLAN VMPS will solve that. Third, what about
> the
> > minority Win98 and Win95 users?
>
> VLANs probably won't solve anything, but then I don't have your earlier
> posts so I may not have the full context..
> This behavor is most commonly seen due to using a Superscope when you
> shouldn't be using one.
>
> We have multiple subnets and all kinds and types of machines and they all
> adjust perfectly fine if moved to a new subnet.
>
> --
> Phillip Windell [MCP, MVP, CCNA]
> www.wandtv.com
> -----------------------------------------------------
> Understanding the ISA 2004 Access Rule Processing
> http://www.isaserver.org/articles/IS...cessRules.html
>
> Microsoft Internet Security & Acceleration Server: Guidance
> http://www.microsoft.com/isaserver/t...dance/2004.asp
> http://www.microsoft.com/isaserver/t...dance/2000.asp
>
> Microsoft Internet Security & Acceleration Server: Partners
> http://www.microsoft.com/isaserver/partners/default.asp
> -----------------------------------------------------
>
>
>
>

"Pagan" <(E-Mail Removed).(nospam)> wrote in message
news:413E9B9B-B016-4658-B25E-(E-Mail Removed)...
> First, can you tell me how to let the clients automatically obtain desired
> IP when they moved to another subnet? Does this revelent to superscope? I
> tried to use or not to ues, same result.

Never use Superscopes. They are for Multi-Nets,...true Multi-Nets are
rare,..you aren't going to have one by accident :-)

> Second, if the firewall can only recognize IP instead of MAC, how to grant
> the clients permition to have Internet access? And these clients are
laptop
> which means they often move to another subnet.

Firewall? It doesn't sound like you are dealing with different
subnets,...it sounds like you are dealing with totally different network
with totally different DHCP Servers. You are going to have to clarify the
exact situation.

Latops will also have a problem if the user only closes the lid or
"hibernates" them or puts them in "standby" rather than fully shutting them
down. The must be fully shutdown/powered off before moving them.

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

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

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