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How is DNS resolution working?

 
 
Ohaya
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      25th Feb 2004
Hi,

We have a small cluster of (all) Win2K Advanced Server machines.

One of the machines (machine A) has 2 NICs, where one of the NICs is
connected to what I will refer to as the "external" network, and the other
NIC is connected to an Ethernet switch (our "internal" network). The IP
addresses for internal network are private network address (192.xx.xx.xx).

We have several other machines (again Win2K AS) connected to that same
switch, and these all have private network addresses (again, 192.xx.xx.xx).

One of these machines (machine B) is configured as a Domain Controller, and
also has DNS Server installed and running. Machine A is a member of the
domain for which machine A is the Domain Controller.

The TCP/IP settings on both machine A and machine B are configured for fixed
IP addresses, and have the DNS server IP addresses fixed to point to machine
B (which has the DNS server).

My expectation was that if I went to machine A, and tried to do a ping of a
machine on the external network using a machine name, that that would fail,
because it would try to use the DNS server on machine B.

But, I was kind of surprised because when I did this, and I did the ping on
a machine on the external network, it was able to resolve the machine name!

I had thought that none of the machines in this configuration would be aware
of any machine names outside of the cluster, and I can't figure out why this
is happening.

Is this maybe because it's using WINS to resolve the machine name?

Any ideas?

Thanks,
Jim


 
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Ohaya
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      25th Feb 2004

"Ohaya" <Ohaya@NO_SPAM.cox.net> wrote in message
news:OgtOHg%23%(E-Mail Removed)...
> Hi,
>
> We have a small cluster of (all) Win2K Advanced Server machines.
>
> One of the machines (machine A) has 2 NICs, where one of the NICs is
> connected to what I will refer to as the "external" network, and the other
> NIC is connected to an Ethernet switch (our "internal" network). The IP
> addresses for internal network are private network address (192.xx.xx.xx).
>
> We have several other machines (again Win2K AS) connected to that same
> switch, and these all have private network addresses (again,

192.xx.xx.xx).
>
> One of these machines (machine B) is configured as a Domain Controller,

and
> also has DNS Server installed and running. Machine A is a member of the
> domain for which machine A is the Domain Controller.
>
> The TCP/IP settings on both machine A and machine B are configured for

fixed
> IP addresses, and have the DNS server IP addresses fixed to point to

machine
> B (which has the DNS server).
>
> My expectation was that if I went to machine A, and tried to do a ping of

a
> machine on the external network using a machine name, that that would

fail,
> because it would try to use the DNS server on machine B.
>
> But, I was kind of surprised because when I did this, and I did the ping

on
> a machine on the external network, it was able to resolve the machine

name!
>
> I had thought that none of the machines in this configuration would be

aware
> of any machine names outside of the cluster, and I can't figure out why

this
> is happening.
>
> Is this maybe because it's using WINS to resolve the machine name?
>
> Any ideas?
>
> Thanks,
> Jim



Sorry. In the above, where it says:

"Machine A is a member of the domain for which machine A is the Domain
Controller."

I should've said:

"Machine A is a member of the domain for which machine B is the Domain
Controller."


 
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Ohaya
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      25th Feb 2004

"Doug Sherman [MVP]" <(E-Mail Removed)> wrote in message
news:u3mEmf$%(E-Mail Removed)...
> The ping command does not depend on DNS. It can use any TCP/IP based name
> resolution, including NetBIOS, hosts files, lmhost files, etc.



Doug,

Apologies if this is a dumb question, but would we have had to specifically
configure the IP address for a WINS server for NetBIOS resolution to be
working on machine A?

I know that we don't have anything in the hosts or lmhosts files on machine
A, and I know they put in the IP address of machine B as in the settings for
the DNS in network properties.

Jim


 
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Ohaya
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      25th Feb 2004

"Ohaya" <Ohaya@NO_SPAM.cox.net> wrote in message
news:uzh$dv$%(E-Mail Removed)...
>
> "Doug Sherman [MVP]" <(E-Mail Removed)> wrote in message
> news:u3mEmf$%(E-Mail Removed)...
> > The ping command does not depend on DNS. It can use any TCP/IP based

name
> > resolution, including NetBIOS, hosts files, lmhost files, etc.

>
>
> Doug,
>
> Apologies if this is a dumb question, but would we have had to

specifically
> configure the IP address for a WINS server for NetBIOS resolution to be
> working on machine A?
>
> I know that we don't have anything in the hosts or lmhosts files on

machine
> A, and I know they put in the IP address of machine B as in the settings

for
> the DNS in network properties.
>
> Jim



Hi,

I have to stop doing this, but I need to correct my post above.

What I meant to ask was wouldn't we have had to specifically configure
machine A to point to a WINS server for NetBIOS name resolution to be
working?

I know that on machine A, we put in a fixed IP address pointing to machine B
for the DNS, and I know that we don't have a hosts or lmhosts files, and I'm
pretty sure that we didn't configure any IP address for WINS server (at
least not on purpose).

So, what's puzzling me is if the possible name resolution mechanisms on
machine A are DNS, hosts, lmhosts, NetBIOS (not in that order), and we don't
have any of them configured on purpose except for DNS, and our DNS server on
machine B is only on a private network, how is the name resolution
succeeding???

Jim


 
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Doug Sherman [MVP]
Guest
Posts: n/a
 
      26th Feb 2004
The ping command does not depend on DNS. It can use any TCP/IP based name
resolution, including NetBIOS, hosts files, lmhost files, etc.

Doug Sherman
MCSE Win2k/NT4.0, MCSA, MCP+I, MVP

"Ohaya" <Ohaya@NO_SPAM.cox.net> wrote in message
news:OgtOHg##(E-Mail Removed)...
> Hi,
>
> We have a small cluster of (all) Win2K Advanced Server machines.
>
> One of the machines (machine A) has 2 NICs, where one of the NICs is
> connected to what I will refer to as the "external" network, and the other
> NIC is connected to an Ethernet switch (our "internal" network). The IP
> addresses for internal network are private network address (192.xx.xx.xx).
>
> We have several other machines (again Win2K AS) connected to that same
> switch, and these all have private network addresses (again,

192.xx.xx.xx).
>
> One of these machines (machine B) is configured as a Domain Controller,

and
> also has DNS Server installed and running. Machine A is a member of the
> domain for which machine A is the Domain Controller.
>
> The TCP/IP settings on both machine A and machine B are configured for

fixed
> IP addresses, and have the DNS server IP addresses fixed to point to

machine
> B (which has the DNS server).
>
> My expectation was that if I went to machine A, and tried to do a ping of

a
> machine on the external network using a machine name, that that would

fail,
> because it would try to use the DNS server on machine B.
>
> But, I was kind of surprised because when I did this, and I did the ping

on
> a machine on the external network, it was able to resolve the machine

name!
>
> I had thought that none of the machines in this configuration would be

aware
> of any machine names outside of the cluster, and I can't figure out why

this
> is happening.
>
> Is this maybe because it's using WINS to resolve the machine name?
>
> Any ideas?
>
> Thanks,
> Jim
>
>



 
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Ace Fekay [MVP]
Guest
Posts: n/a
 
      26th Feb 2004
In news:u9IDn5$%(E-Mail Removed),
Ohaya <Ohaya@NO_SPAM.cox.net> posted their thoughts, then I offered mine
> "Ohaya" <Ohaya@NO_SPAM.cox.net> wrote in message
> news:uzh$dv$%(E-Mail Removed)...
>>
>> "Doug Sherman [MVP]" <(E-Mail Removed)> wrote in
>> message news:u3mEmf$%(E-Mail Removed)...
>>> The ping command does not depend on DNS. It can use any TCP/IP
>>> based name resolution, including NetBIOS, hosts files, lmhost
>>> files, etc.

>>
>>
>> Doug,
>>
>> Apologies if this is a dumb question, but would we have had to
>> specifically configure the IP address for a WINS server for NetBIOS
>> resolution to be working on machine A?
>>
>> I know that we don't have anything in the hosts or lmhosts files on
>> machine A, and I know they put in the IP address of machine B as in
>> the settings for the DNS in network properties.
>>
>> Jim

>
>
> Hi,
>
> I have to stop doing this, but I need to correct my post above.
>
> What I meant to ask was wouldn't we have had to specifically configure
> machine A to point to a WINS server for NetBIOS name resolution to be
> working?
>
> I know that on machine A, we put in a fixed IP address pointing to
> machine B for the DNS, and I know that we don't have a hosts or
> lmhosts files, and I'm pretty sure that we didn't configure any IP
> address for WINS server (at least not on purpose).
>
> So, what's puzzling me is if the possible name resolution mechanisms
> on machine A are DNS, hosts, lmhosts, NetBIOS (not in that order),
> and we don't have any of them configured on purpose except for DNS,
> and our DNS server on machine B is only on a private network, how is
> the name resolution succeeding???
>
> Jim


If machine A (if I got your topology right) is using WINS and the host on
the external subnet is in WINS, and you are pinging by it's single host name
(not the whole FQDN), then yes, it's using WINS. If not, since the subnet is
directly connected, then it's going to broadcast on that subnet for the
name. If using WINS, pinging a single name will check LMHOSTS first then
WINS, but all before DNS.

--
Regards,
Ace

Please direct all replies to the newsgroup so all can benefit.
This posting is provided "AS IS" with no warranties.

Ace Fekay, MCSE 2000, MCSE+I, MCSA, MCT, MVP
Microsoft Windows MVP - Active Directory
--
=================================


 
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Ohaya
Guest
Posts: n/a
 
      26th Feb 2004

"Ace Fekay [MVP]"
<PleaseSubstituteMyActualFirstName&(E-Mail Removed)> wrote in
message news:%23g2hDxB$(E-Mail Removed)...
> In news:u9IDn5$%(E-Mail Removed),
> Ohaya <Ohaya@NO_SPAM.cox.net> posted their thoughts, then I offered mine
> > "Ohaya" <Ohaya@NO_SPAM.cox.net> wrote in message
> > news:uzh$dv$%(E-Mail Removed)...
> >>
> >> "Doug Sherman [MVP]" <(E-Mail Removed)> wrote in
> >> message news:u3mEmf$%(E-Mail Removed)...
> >>> The ping command does not depend on DNS. It can use any TCP/IP
> >>> based name resolution, including NetBIOS, hosts files, lmhost
> >>> files, etc.
> >>
> >>
> >> Doug,
> >>
> >> Apologies if this is a dumb question, but would we have had to
> >> specifically configure the IP address for a WINS server for NetBIOS
> >> resolution to be working on machine A?
> >>
> >> I know that we don't have anything in the hosts or lmhosts files on
> >> machine A, and I know they put in the IP address of machine B as in
> >> the settings for the DNS in network properties.
> >>
> >> Jim

> >
> >
> > Hi,
> >
> > I have to stop doing this, but I need to correct my post above.
> >
> > What I meant to ask was wouldn't we have had to specifically configure
> > machine A to point to a WINS server for NetBIOS name resolution to be
> > working?
> >
> > I know that on machine A, we put in a fixed IP address pointing to
> > machine B for the DNS, and I know that we don't have a hosts or
> > lmhosts files, and I'm pretty sure that we didn't configure any IP
> > address for WINS server (at least not on purpose).
> >
> > So, what's puzzling me is if the possible name resolution mechanisms
> > on machine A are DNS, hosts, lmhosts, NetBIOS (not in that order),
> > and we don't have any of them configured on purpose except for DNS,
> > and our DNS server on machine B is only on a private network, how is
> > the name resolution succeeding???
> >
> > Jim

>
> If machine A (if I got your topology right) is using WINS and the host on
> the external subnet is in WINS, and you are pinging by it's single host

name
> (not the whole FQDN), then yes, it's using WINS. If not, since the subnet

is
> directly connected, then it's going to broadcast on that subnet for the
> name. If using WINS, pinging a single name will check LMHOSTS first then
> WINS, but all before DNS.
>



Ace,

I should've mentioned this. When we did the ping, we used the FQDN of the
host on the external network (e.g., thehost.whatever.com).

Since we were using the external host's FQDN, would the ping still have
caused the broadcast to the external network for the name?

Or, would it only do this broadcast if we had pinged using the hostname
(e.g., thehost)?


I just thought about one other aspect about all of this that I'm starting to
wonder about that might have a bearing on all of this...

This is going to get a bit complicated, so here's what the network config
looks like:

|
|
+---- Machine A ---- Switch ----+----
| |
E | Machine B
x----+ [Domain Controller]
t |
|
+--- ExtDNS
|
|

Machine B = Domain Controller (domain name "test.foo.com")
Machine A = Member (joined to Windows domain "test.foo.com")

ExtDNS = a DNS server on external network, which does DNS for "foo.com"
Ext = a machine on the external network (ExtDNS DNS name=ext.test.foo.com)

Machine A's IP address is registered in the ExtDNS DNS server, with the name
"whatever.test.foo.com".

In other words, if you were on machine "Ext", and pinged
"whatever.test.foo.com", you would end up pinging the external interface of
machine A.

Now, we installed Machine B first, and when we installed Win2K on Machine B,
we set the machine name as "data" and the domain name as "test.foo.com". In
other words the FQDN for machine B from the internal network is
"data.test.foo.com".

I think, based on a thread i posted awhile ago, that we could've picked just
about anything for the domain name (e.g., joe.whatever.foo), but we just
happened to pick "test.foo.com".

We then installed Win2K on Machine A (the member server), and we set the
machine name as "web", and made it a member of (i.e., we joined it to)
domain "test.foo.com". In other words, the FQDN for machine A from the
internal network is "web.test.foo.com".

If you look in the DNS server on machine B, you'll see that both
"web.test.foo.com" and "data.test.foo.com" are registered, and have
"192.xx.xx.xx" IP addresses.

If you ping "web.test.foo.com" from machine B, it resolves to the internal
("192.xx.xx.xx") IP address of machine A.

If you ping "data.test.foo.com" from machine A, it resolves to the IP
address of machine B.


Again, machine B is the Domain Controller, and also has DNS Server running
on it. Machine A is a member server, joined to the domain "test.foo.com"
(whose Domain Controller is machine B).

Here's where this is going to begin sounding strange...

It just happens that on the external network, there is a Windows domain
named "foo.com".

But, remember, our machine A is joined to the domain for which machine B is
the domain controller, not that other Windows domain that is on the external
network.


I'm probably going to muddle this question, but what I'm wondering is if
there is something strange going on with the name resolution when we ping
from machine A because we just happen to pick the name of the "internal"
Windows domain such that that Windows domain's root ("test.com") is the
same as the name of the Windows domain on the external network???

Jim


 
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Ohaya
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Posts: n/a
 
      26th Feb 2004
Hi,

I want to re-word/simplify the last part of my earlier post/question.

First, here's the network configuration:

> |
> |
> +---- Machine A ---- Switch ----+----
> | "web" |
> E | Registered in ExtDNS Machine B
> x----+ as "whatever.foo.com" [Domain Controller "foo.com"]
> t | [DNS entry points "data"
> | to Machine B] [DNS server]
> |
> |
> +--- ExtDNS [hosts DNS domain "foo.com"]
> | [DNS server]
> | [hosts DNS domain "foo.com"]
> |
>
> Machine B = Domain Controller (domain name "foo.com")
> Machine A = Member (joined to Windows domain "foo.com")
>
> ExtDNS = a DNS server on external network, which does DNS for "foo.com"
> Ext = a machine on the external network (ExtDNS DNS name=ext.foo.com)



In the last part of my earlier post, I'm wondering if, with the above
network configuration, it might be possible that when I do a "ping
ext.foo.com" from Machine A, it might be getting confused (because the
suffix for the external network just happens to be the same as the suffix
that we assigned to Machine A), and using NetBIOS name resolution so that it
might be doing a broadcast to the external network to resolve "ext.foo.com"
instead of simply failing the name resolution?

Jim


 
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Ace Fekay [MVP]
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Posts: n/a
 
      27th Feb 2004
In news:eEJhKIH$(E-Mail Removed),
Ohaya <Ohaya@NO_SPAM.cox.net> posted their thoughts, then I offered mine
> Hi,
>
> I want to re-word/simplify the last part of my earlier post/question.
>
> First, here's the network configuration:
>
>> |
>> |
>> +---- Machine A ---- Switch ----+----
>> | "web" |
>> E | Registered in ExtDNS Machine B
>> x----+ as "whatever.foo.com" [Domain Controller "foo.com"]
>> t | [DNS entry points "data"
>> | to Machine B] [DNS server]
>> |
>> |
>> +--- ExtDNS [hosts DNS domain
>> "foo.com"] | [DNS server]
>> | [hosts DNS domain "foo.com"]
>> |
>>
>> Machine B = Domain Controller (domain name "foo.com")
>> Machine A = Member (joined to Windows domain "foo.com")
>>
>> ExtDNS = a DNS server on external network, which does DNS for
>> "foo.com" Ext = a machine on the external network (ExtDNS DNS
>> name=ext.foo.com)

>
>
> In the last part of my earlier post, I'm wondering if, with the above
> network configuration, it might be possible that when I do a "ping
> ext.foo.com" from Machine A, it might be getting confused (because the
> suffix for the external network just happens to be the same as the
> suffix that we assigned to Machine A), and using NetBIOS name
> resolution so that it might be doing a broadcast to the external
> network to resolve "ext.foo.com" instead of simply failing the name
> resolution?
>
> Jim


I'll need to see an ipconfig /all from both A and B. I'm thinking that you
are using both DNS addresses in your IP properties, unless I missed that in
your posts.

--
Regards,
Ace

Please direct all replies to the newsgroup so all can benefit.
This posting is provided "AS IS" with no warranties.

Ace Fekay, MCSE 2000, MCSE+I, MCSA, MCT, MVP
Microsoft Windows MVP - Active Directory
--
=================================


 
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Ace Fekay [MVP]
Guest
Posts: n/a
 
      27th Feb 2004
In news:O3osOZC$(E-Mail Removed),
Ohaya <Ohaya@NO_SPAM.cox.net> posted their thoughts, then I offered mine

> Ace,
>
> I should've mentioned this. When we did the ping, we used the FQDN
> of the host on the external network (e.g., thehost.whatever.com).
>
> Since we were using the external host's FQDN, would the ping still
> have caused the broadcast to the external network for the name?


No, FQDN pings do NOT use broadcasts.

>
> Or, would it only do this broadcast if we had pinged using the
> hostname (e.g., thehost)?


Yes


>
>
> I just thought about one other aspect about all of this that I'm
> starting to wonder about that might have a bearing on all of this...
>
> This is going to get a bit complicated, so here's what the network
> config looks like:
>
> |
> |
> +---- Machine A ---- Switch ----+----
> | |
> E | Machine B
> x----+ [Domain Controller]
> t |
> |
> +--- ExtDNS
> |
> |
>
> Machine B = Domain Controller (domain name "test.foo.com")
> Machine A = Member (joined to Windows domain "test.foo.com")
>
> ExtDNS = a DNS server on external network, which does DNS for
> "foo.com"
> Ext = a machine on the external network (ExtDNS DNS
> name=ext.test.foo.com)
>
> Machine A's IP address is registered in the ExtDNS DNS server, with
> the name "whatever.test.foo.com".
>
> In other words, if you were on machine "Ext", and pinged
> "whatever.test.foo.com", you would end up pinging the external
> interface of machine A.


That would make sense.


>
> Now, we installed Machine B first, and when we installed Win2K on
> Machine B, we set the machine name as "data" and the domain name as
> "test.foo.com". In other words the FQDN for machine B from the
> internal network is "data.test.foo.com".
>
> I think, based on a thread i posted awhile ago, that we could've
> picked just about anything for the domain name (e.g.,
> joe.whatever.foo), but we just happened to pick "test.foo.com".
>
> We then installed Win2K on Machine A (the member server), and we set
> the machine name as "web", and made it a member of (i.e., we joined
> it to) domain "test.foo.com". In other words, the FQDN for machine A
> from the internal network is "web.test.foo.com".



I'm thinking you are providing both DNS addresses (internal and external) on
the A machine in it's IP properties. Not a good thing. Need to keep it
consistent.


>
> If you look in the DNS server on machine B, you'll see that both
> "web.test.foo.com" and "data.test.foo.com" are registered, and have
> "192.xx.xx.xx" IP addresses.
>
> If you ping "web.test.foo.com" from machine B, it resolves to the
> internal ("192.xx.xx.xx") IP address of machine A.
>
> If you ping "data.test.foo.com" from machine A, it resolves to the IP
> address of machine B.
>
>
> Again, machine B is the Domain Controller, and also has DNS Server
> running on it. Machine A is a member server, joined to the domain
> "test.foo.com" (whose Domain Controller is machine B).
>
> Here's where this is going to begin sounding strange...
>
> It just happens that on the external network, there is a Windows
> domain named "foo.com".
>
> But, remember, our machine A is joined to the domain for which
> machine B is the domain controller, not that other Windows domain
> that is on the external network.
>
>
> I'm probably going to muddle this question, but what I'm wondering is
> if there is something strange going on with the name resolution when
> we ping from machine A because we just happen to pick the name of the
> "internal" Windows domain such that that Windows domain's root
> ("test.com") is the same as the name of the Windows domain on the
> external network???
>
> Jim


Let us see an ipconfig /all from both machines please.

--
Regards,
Ace

Please direct all replies to the newsgroup so all can benefit.
This posting is provided "AS IS" with no warranties.

Ace Fekay, MCSE 2000, MCSE+I, MCSA, MCT, MVP
Microsoft Windows MVP - Active Directory
--
=================================


 
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