Any Way to Not Assign DNS Name to IP Address?

I have a DHCP server that I am trying to add a second port on, to assign
different DHCP settings to a separate network with its own DHCP Scope. I
want this new ethernet to *only* be used for DHCP. In an ideal world, I
would not even enable IP on this adapter, and would like it to only respond
to DHCP requests. Unfortunately, the Microsoft DHCP server has the
unfortunate feature that you assign DHCP scopes at the server level by IP
addresses of the network interfaces, rather than by the network interface
names. It would have been nice to assign a particular ethernet interface
to the scope I wanted, and deactivate all TCP/IP on that adapter.

In the meantime, the new ethernet does have an IP address, and as a result
DNS is now resolving the DHCP server to both of those IPs. This is causing
a number of problems since that server is also a file server and we would
prefer all access to that server to go through a firewall on a single
controlled segment. We disable file sharing on the other segments, but
hosts on the new DHCP segment use DNS to resolve the file server name and
attempt file share access on the wrong network address.

Is there a way to control DHCP so that the hostname used for the new DHCP
segment on the DHCP server will be some different name than the default
hostname used on other segments?

--
Will

You do not need to have a second NIC in the DHCP server machine. All
that you need is a machine in that segment which can do DHCP relay. The
relay server has an IP in the new subnet. It receives the broadcast request
and forwards it directly to the DHCP server. DHCP allocates an IP address in
the same IP subnet as the relay agent.

Will wrote:
> I have a DHCP server that I am trying to add a second port on, to
> assign different DHCP settings to a separate network with its own
> DHCP Scope. I want this new ethernet to *only* be used for DHCP.
> In an ideal world, I would not even enable IP on this adapter, and
> would like it to only respond to DHCP requests. Unfortunately, the
> Microsoft DHCP server has the unfortunate feature that you assign
> DHCP scopes at the server level by IP addresses of the network
> interfaces, rather than by the network interface names. It would
> have been nice to assign a particular ethernet interface to the scope
> I wanted, and deactivate all TCP/IP on that adapter.
>
> In the meantime, the new ethernet does have an IP address, and as a
> result DNS is now resolving the DHCP server to both of those IPs.
> This is causing a number of problems since that server is also a file
> server and we would prefer all access to that server to go through a
> firewall on a single controlled segment. We disable file sharing on
> the other segments, but hosts on the new DHCP segment use DNS to
> resolve the file server name and attempt file share access on the
> wrong network address.
>
> Is there a way to control DHCP so that the hostname used for the new
> DHCP segment on the DHCP server will be some different name than the
> default hostname used on other segments?

We want each segment to receive different DHCP settings. The default
routers are different for each segment, for example.

This requires differerent DHCP Scopes, and you cannot have two DHCP Scopes
for the same network. Microsoft requires each scope to be on a different
port of the DHCP server.

So, no, a DHCP relay is not a solution for the requirement I originally put
forward.

--
Will


"Bill Grant" <not.available@online> wrote in message
news:(E-Mail Removed)...
> You do not need to have a second NIC in the DHCP server machine. All
> that you need is a machine in that segment which can do DHCP relay. The
> relay server has an IP in the new subnet. It receives the broadcast
request
> and forwards it directly to the DHCP server. DHCP allocates an IP address
in
> the same IP subnet as the relay agent.
>
> Will wrote:
> > I have a DHCP server that I am trying to add a second port on, to
> > assign different DHCP settings to a separate network with its own
> > DHCP Scope. I want this new ethernet to *only* be used for DHCP.
> > In an ideal world, I would not even enable IP on this adapter, and
> > would like it to only respond to DHCP requests. Unfortunately, the
> > Microsoft DHCP server has the unfortunate feature that you assign
> > DHCP scopes at the server level by IP addresses of the network
> > interfaces, rather than by the network interface names. It would
> > have been nice to assign a particular ethernet interface to the scope
> > I wanted, and deactivate all TCP/IP on that adapter.
> >
> > In the meantime, the new ethernet does have an IP address, and as a
> > result DNS is now resolving the DHCP server to both of those IPs.
> > This is causing a number of problems since that server is also a file
> > server and we would prefer all access to that server to go through a
> > firewall on a single controlled segment. We disable file sharing on
> > the other segments, but hosts on the new DHCP segment use DNS to
> > resolve the file server name and attempt file share access on the
> > wrong network address.
> >
> > Is there a way to control DHCP so that the hostname used for the new
> > DHCP segment on the DHCP server will be some different name than the
> > default hostname used on other segments?
>
>

Who told you that you cannot have two or more scopes for the same
network? It is pretty much standard practice to have multiple scopes on a
DHCP server and use DHCP relay to allocate addresses to different IP subnets
on different segments of the network.


Will wrote:
> We want each segment to receive different DHCP settings. The default
> routers are different for each segment, for example.
>
> This requires differerent DHCP Scopes, and you cannot have two DHCP
> Scopes for the same network. Microsoft requires each scope to be
> on a different port of the DHCP server.
>
> So, no, a DHCP relay is not a solution for the requirement I
> originally put forward.
>
>
> "Bill Grant" <not.available@online> wrote in message
> news:(E-Mail Removed)...
>> You do not need to have a second NIC in the DHCP server machine.
>> All that you need is a machine in that segment which can do DHCP
>> relay. The relay server has an IP in the new subnet. It receives the
>> broadcast request and forwards it directly to the DHCP server. DHCP
>> allocates an IP address in the same IP subnet as the relay agent.
>>
>> Will wrote:
>>> I have a DHCP server that I am trying to add a second port on, to
>>> assign different DHCP settings to a separate network with its own
>>> DHCP Scope. I want this new ethernet to *only* be used for DHCP.
>>> In an ideal world, I would not even enable IP on this adapter, and
>>> would like it to only respond to DHCP requests. Unfortunately, the
>>> Microsoft DHCP server has the unfortunate feature that you assign
>>> DHCP scopes at the server level by IP addresses of the network
>>> interfaces, rather than by the network interface names. It would
>>> have been nice to assign a particular ethernet interface to the
>>> scope I wanted, and deactivate all TCP/IP on that adapter.
>>>
>>> In the meantime, the new ethernet does have an IP address, and as a
>>> result DNS is now resolving the DHCP server to both of those IPs.
>>> This is causing a number of problems since that server is also a
>>> file server and we would prefer all access to that server to go
>>> through a firewall on a single controlled segment. We disable
>>> file sharing on the other segments, but hosts on the new DHCP
>>> segment use DNS to resolve the file server name and attempt file
>>> share access on the wrong network address.
>>>
>>> Is there a way to control DHCP so that the hostname used for the new
>>> DHCP segment on the DHCP server will be some different name than the
>>> default hostname used on other segments?

"Will" <westes-(E-Mail Removed)> wrote in message
news:246dnU3sTKGCqsDZRVn-(E-Mail Removed)...
> I have a DHCP server that I am trying to add a second port on, to assign

You don't add "ports" to DHCP.

> want this new ethernet to *only* be used for DHCP. In an ideal world, I
> would not even enable IP on this adapter, and would like it to only
respond
> to DHCP requests.

How are you supposed to not have TCP/IP in the adapter when DHCP is all
about TCP/IP?

> Unfortunately, the Microsoft DHCP server has the
> unfortunate feature that you assign DHCP scopes at the server level by IP
> addresses of the network interfaces, rather than by the network interface
> names.

No that isn't the case.

> It would have been nice to assign a particular ethernet interface
> to the scope I wanted, and deactivate all TCP/IP on that adapter.

You don't "assign" interfaces to scopes to begin with,..it's irrelevant.

> In the meantime, the new ethernet does have an IP address, and as a result
> DNS is now resolving the DHCP server to both of those IPs. This is
causing
> a number of problems since that server is also a file server and we would
> prefer all access to that server to go through a firewall on a single
> controlled segment.

What does the firewall have to do with it? You aren't supposed to have two
nics in a machine when they both use an IP from the same subnet,...to begin
with.

> Is there a way to control DHCP so that the hostname used for the new DHCP
> segment on the DHCP server will be some different name than the default
> hostname used on other segments?

That is totally irrelevant. The "name" means nothing, is never user for
anything related to DHCP.

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

"Bill Grant" <not.available@online> wrote in message
news:#Qx#(E-Mail Removed)...
> Who told you that you cannot have two or more scopes for the same
> network? It is pretty much standard practice to have multiple scopes on a
> DHCP server and use DHCP relay to allocate addresses to different IP
subnets
> on different segments of the network.

This is exactly what I was trying to say. What did you think I was saying
instead? I never said you could not have multiple scopes on a *server*.

What I did say was that Microsoft DHCP Server does not allow multiple scopes
*for the same network* . By network I meant subnet. If I'm using terms
in a sloppy way, sorry, try to help focus my meaning, but don't distort it.
So the Class C 172.16.10.0 can have a scope and the Class C 172.16.11.0 can
have a scope, with both scopes on a single DHCP server. But you cannot
have two scopes competing on the same Class C network 172.16.10.0.

As a practical matter, a single subnet is usually defined on one port of an
ethernet adapter, but after some experimenting I now see you can just
multihome a single port, so sorry for not expanding on that. If I don't
have multiple ethernet ports on my DHCP server, each port associated with
one and only one subnet and scope, how can I guarantee that any arbitrary
host grabs an IP from the correct scope? If you can help me understand how
I can have multiple scopes and at the same time not expand the number of IP
addresses on any host adapter on the DHCP server, that will solve my
problem.

Any solution that requires a new IP on the DHCP server causes me problems,
because the DHCP server is also a file server and hosts will resolve its
name to multiple IPs, some of which they cannot reach.

--
Will


>
>
> Will wrote:
> > We want each segment to receive different DHCP settings. The default
> > routers are different for each segment, for example.
> >
> > This requires differerent DHCP Scopes, and you cannot have two DHCP
> > Scopes for the same network. Microsoft requires each scope to be
> > on a different port of the DHCP server.
> >
> > So, no, a DHCP relay is not a solution for the requirement I
> > originally put forward.
> >
> >
> > "Bill Grant" <not.available@online> wrote in message
> > news:(E-Mail Removed)...
> >> You do not need to have a second NIC in the DHCP server machine.
> >> All that you need is a machine in that segment which can do DHCP
> >> relay. The relay server has an IP in the new subnet. It receives the
> >> broadcast request and forwards it directly to the DHCP server. DHCP
> >> allocates an IP address in the same IP subnet as the relay agent.
> >>
> >> Will wrote:
> >>> I have a DHCP server that I am trying to add a second port on, to
> >>> assign different DHCP settings to a separate network with its own
> >>> DHCP Scope. I want this new ethernet to *only* be used for DHCP.
> >>> In an ideal world, I would not even enable IP on this adapter, and
> >>> would like it to only respond to DHCP requests. Unfortunately, the
> >>> Microsoft DHCP server has the unfortunate feature that you assign
> >>> DHCP scopes at the server level by IP addresses of the network
> >>> interfaces, rather than by the network interface names. It would
> >>> have been nice to assign a particular ethernet interface to the
> >>> scope I wanted, and deactivate all TCP/IP on that adapter.
> >>>
> >>> In the meantime, the new ethernet does have an IP address, and as a
> >>> result DNS is now resolving the DHCP server to both of those IPs.
> >>> This is causing a number of problems since that server is also a
> >>> file server and we would prefer all access to that server to go
> >>> through a firewall on a single controlled segment. We disable
> >>> file sharing on the other segments, but hosts on the new DHCP
> >>> segment use DNS to resolve the file server name and attempt file
> >>> share access on the wrong network address.
> >>>
> >>> Is there a way to control DHCP so that the hostname used for the new
> >>> DHCP segment on the DHCP server will be some different name than the
> >>> default hostname used on other segments?
>
>

"Phillip Windell" <@.> wrote in message
news:#(E-Mail Removed)...
> "Will" <westes-(E-Mail Removed)> wrote in message
> news:246dnU3sTKGCqsDZRVn-(E-Mail Removed)...
> > I have a DHCP server that I am trying to add a second port on, to assign
>
> You don't add "ports" to DHCP.

I didn't say you add ports to DHCP. I said I have a DHCP Server (i.e., a
computer that runs the application DHCP Server). Windows servers have
subnets which are assigned to host adapters. For several reasons I was
choosing to assign each subnet to a single ethernet port on a host adapter.
So adding a subnet required the use of an additional ethernet port on the
DHCP Server computer.


> How are you supposed to not have TCP/IP in the adapter when DHCP is all
> about TCP/IP?

DHCP is about how a client that has no IP address obtains one. As far as I
can tell from the specs, DHCP is using UDP packets but the DHCP protocol is
not itself TCP/IP based. Those UDP packets do not route using IP and short
of using a relay agent the DHCP client and server must be on the same
segment.

I guess the reason that the TCP/IP protocol must be loaded on the ethernet
adapter in order for the DHCP server to function on that adapter is that
Microsoft's UDP implementation is embedded in that protocol service/stack.
In theory Microsoft could have implemented a special UDP just for DHCP in a
separate protocol, thus allowing an ethernet adapter to serve out IP
addresses to a network without itself consuming an IP address. That would
have a lot of desirable security benefits as well. But they didn't do that.


> > Unfortunately, the Microsoft DHCP server has the
> > unfortunate feature that you assign DHCP scopes at the server level by
IP
> > addresses of the network interfaces, rather than by the network
interface
> > names.
>
> No that isn't the case.

From the Microsoft DHCP Concepts help file in Windows 2000:
"A DHCP scope consists of a pool of IP addresses on a given subnet.....
Each subnet can have only a single DHCP scope...."

I apologize that I was not very clear, but we implement each subnet on a
separate ethernet port of an ethernet host adapter. So I was using
"network interface" and "subnet" interchangeably. I realize you can
multihome a single interface with multiple subnets. When I did this
however I couldn't control which subnet/scope a given client would be
assigned to, and I need to control that. So we put each subnet onto a
separate network interface. As soon as the DHCP server has more than one
IP address, it's DNS entry resolves to both of those IPs. That creates
problems because that alternate address is not reachable by some of the
clients.


> What does the firewall have to do with it? You aren't supposed to have
two
> nics in a machine when they both use an IP from the same subnet,...to
begin
> with.

I never said that we had two NICs in a machine that use IPs on the same
subnet. We have two NICs in a machine that have different IPs on different
subnets. DNS is resolving the machine's name to those two IPs, and we
would like the machine to be known by a single IP address to the public
network.

--
Will

Fine. What Phillip and I are saying is that you are using the wrong
approach. Multihoming a server will always cause the sorts of problems that
you are seeing. They can be fixed, but it is tedious and unnecessary. Leave
the DHCP server with one NIC and one IP address. Use a server in the second
IP subnet to act as a DHCP relay.

The server with the relay agent will receive the DHCP broadcast on its
local segment. It will contact the DHCP server through the network. The DHCP
server will allocate an IP address from the scope which matches the DHCP
relay machine's IP address/subnet, not the DHCP server's own IP address.

Will wrote:
> "Phillip Windell" <@.> wrote in message
> news:#(E-Mail Removed)...
>> "Will" <westes-(E-Mail Removed)> wrote in message
>> news:246dnU3sTKGCqsDZRVn-(E-Mail Removed)...
>>> I have a DHCP server that I am trying to add a second port on, to
>>> assign
>>
>> You don't add "ports" to DHCP.
>
> I didn't say you add ports to DHCP. I said I have a DHCP Server
> (i.e., a computer that runs the application DHCP Server). Windows
> servers have subnets which are assigned to host adapters. For
> several reasons I was choosing to assign each subnet to a single
> ethernet port on a host adapter. So adding a subnet required the use
> of an additional ethernet port on the DHCP Server computer.
>
>
>> How are you supposed to not have TCP/IP in the adapter when DHCP is
>> all about TCP/IP?
>
> DHCP is about how a client that has no IP address obtains one. As
> far as I can tell from the specs, DHCP is using UDP packets but the
> DHCP protocol is not itself TCP/IP based. Those UDP packets do not
> route using IP and short of using a relay agent the DHCP client and
> server must be on the same segment.
>
> I guess the reason that the TCP/IP protocol must be loaded on the
> ethernet adapter in order for the DHCP server to function on that
> adapter is that Microsoft's UDP implementation is embedded in that
> protocol service/stack. In theory Microsoft could have implemented a
> special UDP just for DHCP in a separate protocol, thus allowing an
> ethernet adapter to serve out IP addresses to a network without
> itself consuming an IP address. That would have a lot of desirable
> security benefits as well. But they didn't do that.
>
>
>>> Unfortunately, the Microsoft DHCP server has the
>>> unfortunate feature that you assign DHCP scopes at the server level
>>> by IP addresses of the network interfaces, rather than by the
>>> network interface names.
>>
>> No that isn't the case.
>
> From the Microsoft DHCP Concepts help file in Windows 2000:
> "A DHCP scope consists of a pool of IP addresses on a given
> subnet..... Each subnet can have only a single DHCP scope...."
>
> I apologize that I was not very clear, but we implement each subnet
> on a separate ethernet port of an ethernet host adapter. So I was
> using "network interface" and "subnet" interchangeably. I realize
> you can multihome a single interface with multiple subnets. When I
> did this however I couldn't control which subnet/scope a given client
> would be assigned to, and I need to control that. So we put each
> subnet onto a separate network interface. As soon as the DHCP
> server has more than one IP address, it's DNS entry resolves to both
> of those IPs. That creates problems because that alternate address
> is not reachable by some of the clients.
>
>
>> What does the firewall have to do with it? You aren't supposed to
>> have two nics in a machine when they both use an IP from the same
>> subnet,...to begin with.
>
> I never said that we had two NICs in a machine that use IPs on the
> same subnet. We have two NICs in a machine that have different IPs
> on different subnets. DNS is resolving the machine's name to those
> two IPs, and we would like the machine to be known by a single IP
> address to the public network.

"Will" <westes-(E-Mail Removed)> wrote in message
news:zZKdnboXBqP3n_3ZRVn-(E-Mail Removed)...
> What I did say was that Microsoft DHCP Server does not allow multiple
scopes
> *for the same network*


Of course you can. They are called Superscopes. You place the multiple
regular Scopes inside the Superscope and the Superscope makes them all
behave as "one". The scopes of course have to be compatible with each other
(same subnet).

> As a practical matter, a single subnet is usually defined on one port of
an
> ethernet adapter, but after some experimenting I now see you can just
> multihome a single port, so sorry for not expanding on that. If I don't
> have multiple ethernet ports on my DHCP server, each port associated with
> one and only one subnet and scope, how can I guarantee that any arbitrary
> host grabs an IP from the correct scope?

You don't. You don't create a situation where that even matters. If you do,
then you are doing it wrong.

The truth is that you should eliminate the multiple Scopes and use one scope
that covers all the IP#s involved. Then you never need a Superscope.

> I can have multiple scopes and at the same time not expand the number of
IP
> addresses on any host adapter on the DHCP server, that will solve my
> problem.

You never do that,.. ever, ...,no matter what. I have no idea what you are
thinking there.

> Any solution that requires a new IP on the DHCP server causes me problems,
> because the DHCP server is also a file server and hosts will resolve its
> name to multiple IPs, some of which they cannot reach.

??? That makes no sense.

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

"Will" <westes-(E-Mail Removed)> wrote in message
news(E-Mail Removed) ...
> computer that runs the application DHCP Server). Windows servers have
> subnets which are assigned to host adapters.

Ok.

> For several reasons I was
> choosing to assign each subnet to a single ethernet port on a host
adapter.
> So adding a subnet required the use of an additional ethernet port on the
> DHCP Server computer.

No it does not.
The IP# of the DHCP Server is irrelevant
The subnet the DHCP exist in is irrelevant
The number of ports, nics, IP#s, whatever, in/on the DHCP box...is
irrelevant.

> > How are you supposed to not have TCP/IP in the adapter when DHCP is all
> > about TCP/IP?
>
> DHCP is about how a client that has no IP address obtains one. As far as
I
> can tell from the specs, DHCP is using UDP packets but the DHCP protocol
is
> not itself TCP/IP based.

TCP/IP encompasses *both* UDP and TCP. Techincally UDP is UDP/IP but that
is never stated that way,...the name TCP/IP covers both of them.

> I guess the reason that the TCP/IP protocol must be loaded on the
ethernet
> adapter in order for the DHCP server to function on that adapter is that
> Microsoft's UDP implementation is embedded in that protocol service/stack.
> In theory Microsoft could have implemented a special UDP just for DHCP in
a
> separate protocol, thus allowing an ethernet adapter to serve out IP
> addresses to a network without itself consuming an IP address. That
would
> have a lot of desirable security benefits as well. But they didn't do
that.

I'm sorry, but that is nonsense. UDP cannot exist without IP,...UDP cannot
exist without IP#s. TCP and UDP are Layer4 protocols and are nearly
identical other than TCP requires acknowledgement and UDP does not. Both of
them run on top of IP which is the Layer3 Protocol the "carries" the Layer4
Protocols (TCP/UDP) inside of it

> I apologize that I was not very clear, but we implement each subnet on a
> separate ethernet port of an ethernet host adapter.

No what you have there is *multiple* Ethernet Adapters on one Physical Card.
Each port is a separate "adapter" just as if it was a separate card in the
machine.

> subnet. We have two NICs in a machine that have different IPs on
different
> subnets. DNS is resolving the machine's name to those two IPs, and we
> would like the machine to be known by a single IP address to the public
> network.

Then stop doing that and run one IP#, one "internface", one subnet. Create
a regular Scope for each subnet on within the DHCP Service. Configure the
LAN Router to forward the DHCP Queries the way it is supposed to be done.
When you do things the way they are supposed to be done you don't have
problems.


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