Multiple Domains on a single physical LAN

While I know it is technically possible, what are the postive/negatives of
sharing a commnon physical LAN on multiple domains.
I have a company that wants to build a second domain onto an existing
address space, 172.19.10.0/24. The assigned and reserved address would be a
mixture from top to bottom.
I read where there are potential authentication problems with the computers
if this infrastructure is built this way.
Looking for advice whether to proceed.

Hello Jay,

You have to use fixed ip addresses for ALL machines, with DHCP it will not
work correct. If you work on the same physical LAN, use at least 2 different
ip ranges for the domains.

BUT you should really better separate the domains, you create your own configuration
mess with using one physical LAN.

Best regards

Meinolf Weber
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> While I know it is technically possible, what are the
> postive/negatives of sharing a commnon physical LAN on multiple
> domains. I have a company that wants to build a second domain onto an
> existing address space, 172.19.10.0/24. The assigned and reserved
> address would be a mixture from top to bottom. I read where there are
> potential authentication problems with the computers if this
> infrastructure is built this way. Looking for advice whether to
> proceed.
>

Jay,
the primary concern is DNS configuration of your clients. In particular, you
should use Group Policy (Computer Configuration\Administrative
Templates\Network\DNS Client) to assign DNS servers and suffixes to client
computers in their respective domains (assuming you are using AD-integrated
DNS). In addition, when using AD-integrated DNS, you might also have an
issue with reverse lookup zones (unless both domains are in the same forest
and you configure these zones to be part of the ForestDNSZones partition)...

hth
Marcin

"Jay" <Jay@discussions.microsoft.com> wrote in message
news:15F86A34-6256-472C-8393-E32BA6A45650@microsoft.com...
> While I know it is technically possible, what are the postive/negatives of
> sharing a commnon physical LAN on multiple domains.
> I have a company that wants to build a second domain onto an existing
> address space, 172.19.10.0/24. The assigned and reserved address would be
> a
> mixture from top to bottom.
> I read where there are potential authentication problems with the
> computers
> if this infrastructure is built this way.
> Looking for advice whether to proceed.

Jay <Jay@discussions.microsoft.com> wrote:
> While I know it is technically possible, what are the
> postive/negatives of sharing a commnon physical LAN on multiple
> domains.
> I have a company that wants to build a second domain onto an existing
> address space, 172.19.10.0/24. The assigned and reserved address
> would be a mixture from top to bottom.
> I read where there are potential authentication problems with the
> computers if this infrastructure is built this way.
> Looking for advice whether to proceed.

What is the reason they want to do this?

There seems to be some concern about multicast resources that exist in old
domain 1 not rendering properly into new domain 2. So the wizards of smart
want to move domain 2 into the same address space as domain 1. I am seeking
advice of the pros and cons before I finalize my response to them.

"Lanwench [MVP - Exchange]" wrote:

> Jay <Jay@discussions.microsoft.com> wrote:
> > While I know it is technically possible, what are the
> > postive/negatives of sharing a commnon physical LAN on multiple
> > domains.
> > I have a company that wants to build a second domain onto an existing
> > address space, 172.19.10.0/24. The assigned and reserved address
> > would be a mixture from top to bottom.
> > I read where there are potential authentication problems with the
> > computers if this infrastructure is built this way.
> > Looking for advice whether to proceed.
>
> What is the reason they want to do this?
>
>
>

Jay,

Jay schrieb:
> There seems to be some concern about multicast resources that exist in old
> domain 1 not rendering properly into new domain 2. So the wizards of smart
> want to move domain 2 into the same address space as domain 1. I am seeking
> advice of the pros and cons before I finalize my response to them.

Besides DNS and DHCP that should be your concerns, note that within a
common subnet, you won't be able to have dublicate machine names. I've
had that once with a customer. They basically tried to promote a new
domain with a domain controller called "dc1" which basically had the
same name than an already promoted DC of another domain in the same
subnet. NetBIOS names must be unique.

Cheers,
Florian
--
Microsoft MVP - Group Policy
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