DHCP Superscopes

We have recently started using DHCP Superscopes. Since doing this, we have
problems with PC that roam from one subnet to another. The DHCP server seems
to igore the Gateway IP Address(GIADDR) field in the DHCP packet. An example
of this is, if a PC has a current valid lease or has a reservation in one
subnet but then roams to a diferent subnet, the DHCP server ACK's the packet
from the pc trying to renew it's old lease giving it an address from the
previous subnet. Instead, the appropriate response would be to NACK the
packet and giving the pc an new address based on the address of the GIADDR
field, which has the address of the relay agent, giving it a new address from
the new subnet.

Is there some kind of option or registry key entry that would make the DHCP
server not ignore the GIADDR field?

"Enrique" <(E-Mail Removed)> wrote in message
news:940C9F37-4A52-4352-8559-(E-Mail Removed)...
> We have recently started using DHCP Superscopes. Since doing this, we
have
> problems with PC that roam from one subnet to another. The DHCP server
seems
> to igore the Gateway IP Address(GIADDR) field in the DHCP packet. An
example
> of this is, if a PC has a current valid lease or has a reservation in one
> subnet but then roams to a diferent subnet, the DHCP server ACK's the
packet
> from the pc trying to renew it's old lease giving it an address from the
> previous subnet. Instead, the appropriate response would be to NACK the
> packet and giving the pc an new address based on the address of the GIADDR
> field, which has the address of the relay agent, giving it a new address
from
> the new subnet.

How are you using SuperScopes (which should be called
ScopeGroups but that is not MS's fault, it's standard DHCP.)

A superscope(group) is for a MULTINET, to group IP subnets
into a single superscope(group) when there is more than one
subnet on a physical segment (broadcast domain.)

Such multinet are an unusual case, usually for when you have
small subnets and need a few extra machines (above the subnet
limit) on one or a few physical segments.

You superscope(group) them to instruct the DHCP server to
treat them as one scope.

> Is there some kind of option or registry key entry that would make the
DHCP
> server not ignore the GIADDR field?

It sounds vaguely as if you might have superscope(grouped)
subnet ranges from OTHER segments.

--
Herb Martin

Can you provide a NetMon sniff and the DHCP config ( Netsh ). If the packet
is actually being Relayed, the GIADDR field should not be ignored.

--
--
Dusty Harper
Microsoft Corporation
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"Enrique" <(E-Mail Removed)> wrote in message
news:940C9F37-4A52-4352-8559-(E-Mail Removed)...
> We have recently started using DHCP Superscopes. Since doing this, we
have
> problems with PC that roam from one subnet to another. The DHCP server
seems
> to igore the Gateway IP Address(GIADDR) field in the DHCP packet. An
example
> of this is, if a PC has a current valid lease or has a reservation in one
> subnet but then roams to a diferent subnet, the DHCP server ACK's the
packet
> from the pc trying to renew it's old lease giving it an address from the
> previous subnet. Instead, the appropriate response would be to NACK the
> packet and giving the pc an new address based on the address of the GIADDR
> field, which has the address of the relay agent, giving it a new address
from
> the new subnet.
>
> Is there some kind of option or registry key entry that would make the
DHCP
> server not ignore the GIADDR field?

> "Enrique" <(E-Mail Removed)> wrote in message
> news:940C9F37-4A52-4352-8559-(E-Mail Removed)...
> > We have recently started using DHCP Superscopes. Since doing this, we
> > have problems with PC that roam from one subnet to another. The DHCP
server
> > .................
> > from the pc trying to renew it's old lease giving it an address from the
> > previous subnet.

Get rid of the Superscopes. That is not what they are for. Use separate
distinct Scope for each subnet. No Superscopes!

Superscopes *combine* multiple scopes into one,...this is the *opposite* of
what you want.

--

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

This brings me to wonder what superscopes are for. When, why, how would one
use a superscope?

"Phillip Windell" <@.> wrote in message
news:ui$tOCM%(E-Mail Removed)...
>> "Enrique" <(E-Mail Removed)> wrote in message
>> news:940C9F37-4A52-4352-8559-(E-Mail Removed)...
>> > We have recently started using DHCP Superscopes. Since doing this, we
>> > have problems with PC that roam from one subnet to another. The DHCP
> server
>> > .................
>> > from the pc trying to renew it's old lease giving it an address from
>> > the
>> > previous subnet.
>
> Get rid of the Superscopes. That is not what they are for. Use separate
> distinct Scope for each subnet. No Superscopes!
>
> Superscopes *combine* multiple scopes into one,...this is the *opposite*
> of
> what you want.
>
> --
>
> Phillip Windell [MCP, MVP, CCNA]
> www.wandtv.com
>
>

"Ray Perkinson" <(E-Mail Removed)> wrote in message
news:e$CbvKU#(E-Mail Removed)...
> This brings me to wonder what superscopes are for. When, why, how would
one
> use a superscope?
>

They are to support multiple scopes on the same
segment (broadcast domain) for those rare times
when you have a MULTINET and wish to use DHCP.

A Multinet is two or more IP subnets occupying the
same segment (broadcast domain.)

Normally IP Subnets and broadcast segments are
in a one to one relationship but this is not an absolute
rule.

Typically this occurs because the IP Subnet only
support a small number of addresses which needs
to be exceeded and so two subnets are place on
that segment without introducing a new router or
router inteface. E.g., 14 addresses allowed but
20 stations are required, so instead of re-architecting
the IP subnet (perhaps worldwide) the segment is
given a second set of 14 addresses.

Another (probably less common reason) is when
addresses from both a public and a private range
co-exist on the same segment.

Today this is much less common due to the prevalence
of NAT to just isolate the private address, map the
public addresses as necessary, and thus just avoid
this issue.


--
Herb Martin


> "Phillip Windell" <@.> wrote in message
> news:ui$tOCM%(E-Mail Removed)...
> >> "Enrique" <(E-Mail Removed)> wrote in message
> >> news:940C9F37-4A52-4352-8559-(E-Mail Removed)...
> >> > We have recently started using DHCP Superscopes. Since doing this,
we
> >> > have problems with PC that roam from one subnet to another. The DHCP
> > server
> >> > .................
> >> > from the pc trying to renew it's old lease giving it an address from
> >> > the
> >> > previous subnet.
> >
> > Get rid of the Superscopes. That is not what they are for. Use separate
> > distinct Scope for each subnet. No Superscopes!
> >
> > Superscopes *combine* multiple scopes into one,...this is the *opposite*
> > of
> > what you want.
> >
> > --
> >
> > Phillip Windell [MCP, MVP, CCNA]
> > www.wandtv.com
> >
> >
>
>

The need for them is rare. Most of the "needs" are due to a bad topology
design in the first place,..that if corrected, eliminates the need for the
Superscope. If people wouldn' design such "odd-ball" topologies as seen in
some of these articles below, they wouldn't need Superscopes. It would seem
that VLANs have eliminated some of the need for Superscopes.

Just use "superscopes" in a Search on MS's site and you will get a lot of
hits.

Here are a few links to articles on them,...I find them rather painful to
follow.

http://www.microsoft.com/resources/d...uperscopes.asp

http://www.microsoft.com/resources/d...b_dhc_opoj.asp

Superscoping vs. Supernetting
http://support.microsoft.com/default...b;en-us;186341

--

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




"Ray Perkinson" <(E-Mail Removed)> wrote in message
news:e$CbvKU%(E-Mail Removed)...
> This brings me to wonder what superscopes are for. When, why, how would
one
> use a superscope?
>
> "Phillip Windell" <@.> wrote in message
> news:ui$tOCM%(E-Mail Removed)...
> >> "Enrique" <(E-Mail Removed)> wrote in message
> >> news:940C9F37-4A52-4352-8559-(E-Mail Removed)...
> >> > We have recently started using DHCP Superscopes. Since doing this,
we
> >> > have problems with PC that roam from one subnet to another. The DHCP
> > server
> >> > .................
> >> > from the pc trying to renew it's old lease giving it an address from
> >> > the
> >> > previous subnet.
> >
> > Get rid of the Superscopes. That is not what they are for. Use separate
> > distinct Scope for each subnet. No Superscopes!
> >
> > Superscopes *combine* multiple scopes into one,...this is the *opposite*
> > of
> > what you want.
> >
> > --
> >
> > Phillip Windell [MCP, MVP, CCNA]
> > www.wandtv.com
> >
> >
>
>

"Phillip Windell" <@.> wrote in message
news:u0y2zMZ#(E-Mail Removed)...
> The need for them is rare. Most of the "needs" are due to a bad topology
> design in the first place,..that if corrected, eliminates the need for the
> Superscope. If people wouldn' design such "odd-ball" topologies as seen in
> some of these articles below, they wouldn't need Superscopes. It would
seem
> that VLANs have eliminated some of the need for Superscopes.
>
> Just use "superscopes" in a Search on MS's site and you will get a lot of
> hits.


Yes, they have. But sometimes (rare, we agree) a
GOOD design incorporates a (very limited) use of
Superscopes.

The classic example is the company with 2000
store locations (2000 wan lines using their own
subnets back to the hubs) where (almost) every
store has less than 14 computers.

BUT, it turns out that the two largest stores are
"double size" having less than 30 computers.

You can add a router, or a router NIC (doesn't
cost much today, but why take the machine apart)
or you can just Multinet, and thus superscope if using
DHCP.

Nothing at all wrong with this design and it saves
a few dollars and some trouble with the hardware.
--
Herb Martin


"Phillip Windell" <@.> wrote in message
news:u0y2zMZ#(E-Mail Removed)...
> The need for them is rare. Most of the "needs" are due to a bad topology
> design in the first place,..that if corrected, eliminates the need for the
> Superscope. If people wouldn' design such "odd-ball" topologies as seen in
> some of these articles below, they wouldn't need Superscopes. It would
seem
> that VLANs have eliminated some of the need for Superscopes.
>
> Just use "superscopes" in a Search on MS's site and you will get a lot of
> hits.
>
> Here are a few links to articles on them,...I find them rather painful to
> follow.
>
>
http://www.microsoft.com/resources/d...Serv/2003/stan
dard/proddocs/en-us/sag_dhcp_imp_usingsuperscopes.asp
>
>
http://www.microsoft.com/resources/d...b_dhc_opoj.asp
>
> Superscoping vs. Supernetting
> http://support.microsoft.com/default...b;en-us;186341
>
> --
>
> Phillip Windell [MCP, MVP, CCNA]
> www.wandtv.com
>
>
>
>
> "Ray Perkinson" <(E-Mail Removed)> wrote in message
> news:e$CbvKU%(E-Mail Removed)...
> > This brings me to wonder what superscopes are for. When, why, how would
> one
> > use a superscope?
> >
> > "Phillip Windell" <@.> wrote in message
> > news:ui$tOCM%(E-Mail Removed)...
> > >> "Enrique" <(E-Mail Removed)> wrote in message
> > >> news:940C9F37-4A52-4352-8559-(E-Mail Removed)...
> > >> > We have recently started using DHCP Superscopes. Since doing this,
> we
> > >> > have problems with PC that roam from one subnet to another. The
DHCP
> > > server
> > >> > .................
> > >> > from the pc trying to renew it's old lease giving it an address
from
> > >> > the
> > >> > previous subnet.
> > >
> > > Get rid of the Superscopes. That is not what they are for. Use
separate
> > > distinct Scope for each subnet. No Superscopes!
> > >
> > > Superscopes *combine* multiple scopes into one,...this is the
*opposite*
> > > of
> > > what you want.
> > >
> > > --
> > >
> > > Phillip Windell [MCP, MVP, CCNA]
> > > www.wandtv.com
> > >
> > >
> >
> >
>
>