Problems assigning IP addresses from DHCP superscopes in VLANs

hi all,

we've got a windows 2003 DHCP server and several VLANs in our company
network. each floor has its own VLAN. Each VLAN has its own DHCP superscope
on a DHCP server. Everything is working fine. If a pc/notebook is connect to
a VLAN (e.g. VLAN 15) it obtains an IP address from the correct superscope
(in this case 10.15.x.x/24). If a pc/notebook is connected to a VLAN (e.g.
16) it obtains an IP address from another superscope (in this case
10.16.x.x/24). so far so good.

Now I've got big problems with "roaming" clients. If a client which obtained
an IP address e.g. in VLAN 15 moves to another floor with VLAN 16 it tries to
get the same IP address than in VLAN 15. The only solution in the moment is
to delete the lease from the DHCP server manually. If the concerning lease is
deleted in the DHCP server (in this case from the superscope of VLAN 15) the
client obtains an IP address from the correct superscope 10.16.x.x/24. when
the client moves again to the other VLAN 15, the lease has to be deleted
again. of course this can not be the solution.

what could be a comfortable solution for both, the client and the
administrators? the best solution of course would be, if the lease is removed
automatically from the server whether if the leasetime is expired (and the
client did not renew it) or if the client is no longer in the concerning
VLAN. (I've already configured a short-term leastime of 1 hour)

THANKS for your support!!

You are not supposed to use Superscopes for that. Superscopes do pretty much
the exact opposite of what you want to do,[...as you are noticing].
Eliminate the Superscope(s), use regular Scopes,...one for each Segment.
Use the full IP Range of each segment in each corresponding Scope and use
Exclusions to limit which addresses are given out.

--

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

I agree you shouldn't use superscopes in this way...

The other way you could do it is create seperate scopes on your DHCP server
and use either the DHCP relay agent on a server on each floor to forward the
requests to a single DHCP server or use RFC-1542 compatbile routers to
forward BOOTP.

"Phillip Windell" wrote:

> You are not supposed to use Superscopes for that. Superscopes do pretty much
> the exact opposite of what you want to do,[...as you are noticing].
> Eliminate the Superscope(s), use regular Scopes,...one for each Segment.
> Use the full IP Range of each segment in each corresponding Scope and use
> Exclusions to limit which addresses are given out.
>
> --
>
> Phillip Windell [MCP, MVP, CCNA]
> www.wandtv.com
>
>
>

Hi Phillip,

thx for your fast answer... OK, I will try to delete all superscopes and
create "normal" scopes - BUT - there is one additional question. I've read
that if I create more than one "normal" scope I would need seperate network
interface cards, especially when I am using VLANs. Otherwise the clients
won't get IP addresses from the correct scope (e.g. clients in 2nd floor and
VLAN 2 should obtain IP addresses from scope 10.43.2.0/24, clients in 3rd
florr and VLAN 3 should obtain IP addresses from scope 10.43.3.0/24 and so
on... - for this function I've read that I have to use superscopes - is that
true?)

Thank you

"Phillip Windell" schrieb:

> You are not supposed to use Superscopes for that. Superscopes do pretty much
> the exact opposite of what you want to do,[...as you are noticing].
> Eliminate the Superscope(s), use regular Scopes,...one for each Segment.
> Use the full IP Range of each segment in each corresponding Scope and use
> Exclusions to limit which addresses are given out.
>
> --
>
> Phillip Windell [MCP, MVP, CCNA]
> www.wandtv.com
>
>
>

"Reinhard Achatz" <(E-Mail Removed)> wrote in
message news:00AB8730-4856-4874-BDDE-(E-Mail Removed)...
> thx for your fast answer... OK, I will try to delete all superscopes and
> create "normal" scopes - BUT - there is one additional question. I've read
> that if I create more than one "normal" scope I would need seperate
network
> interface cards, especially when I am using VLANs. Otherwise the clients

No. It will be fine. The DHCP Server can have a single Nic and a single IP#
on just one of the subnets (doesn't matter which,..pick your favorite). The
router is what forwards the "query" packets from the host to the DHCP across
the subnets. The router includes the proper information in the relay so the
DHCP knows where it came from and the DHCP is smart enough to know what to
do about it.

Do not have the DHCP "live" on more than one subnet at once. Yes (before
anyone "reminds" me) it can be done,...but I am trying to keep things simple
and easier to configure with what I believe will present the least amount to
go wrong.

The fact that you have VLANs doesn't matter, VLAN segments and physical
segment work on the same principle so it just doesn't matter. The key is to
not have misconfigured VLANs so you don't end up blaming the DHCP for
something that is the VLAN config's fault.

--

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

hi phillip,

sorry for my late answer, but I wanted to thank you for your hints. I
deleted all superscopes (it was pretty easy... no IP leases or configuration
was lost.... just right click :-)

now everything is working fine. every client is getting its own IP address
in each VLAN. the DHCP server keeps it also when the client is in another
VLAN, so the client will get the same IP address when he comes back to a
VLAN... perfectly :-)

"Phillip Windell" wrote:

> "Reinhard Achatz" <(E-Mail Removed)> wrote in
> message news:00AB8730-4856-4874-BDDE-(E-Mail Removed)...
> > thx for your fast answer... OK, I will try to delete all superscopes and
> > create "normal" scopes - BUT - there is one additional question. I've read
> > that if I create more than one "normal" scope I would need seperate
> network
> > interface cards, especially when I am using VLANs. Otherwise the clients
>
> No. It will be fine. The DHCP Server can have a single Nic and a single IP#
> on just one of the subnets (doesn't matter which,..pick your favorite). The
> router is what forwards the "query" packets from the host to the DHCP across
> the subnets. The router includes the proper information in the relay so the
> DHCP knows where it came from and the DHCP is smart enough to know what to
> do about it.
>
> Do not have the DHCP "live" on more than one subnet at once. Yes (before
> anyone "reminds" me) it can be done,...but I am trying to keep things simple
> and easier to configure with what I believe will present the least amount to
> go wrong.
>
> The fact that you have VLANs doesn't matter, VLAN segments and physical
> segment work on the same principle so it just doesn't matter. The key is to
> not have misconfigured VLANs so you don't end up blaming the DHCP for
> something that is the VLAN config's fault.
>
> --
>
> Phillip Windell [MCP, MVP, CCNA]
> www.wandtv.com
>
>
>