Routing with Multiple NICs.

I have a server 2003 machine that runs Exchange server. This server has 2
network cards. [LAN] card is obviously connected to a network switch that
all users in the office use (since the server is also the AD domain
controller) and this network also has a cable modem on it. The WAN card in
this machine connects to a network switch that is then connected to a DSL
modem (and this card is the only one that has a gateway defined). The
reason for this is that all email comes in through the static IP address of
the DSL modem and when we send email - it goes out through the DSL line.

Server 2003 is running a DHCP server that hands out IP address and sets
everyones DNS to that of the server and their gateway to that of the cable
modem that is on the LAN in the office. We prefer everyone in office use
the cable modem and that the DSL line is only used for Email (in a
nutshell). We have noticed that when users change their DNS not to use that
of the server - their internet speed is really fast! *But* when we go with
what DHCP hands out (using DNS on the server) everything runs really slow.
I used performance monitor to check DNS and it is running fine. I then
disconnected the DSL from the server and disabled that NIC and all the
machines in the office started to move a lot faster.

I concluded that I have some strange routing issue going on or something -
because of the way I have the server set to use a different gateway that the
clients in the office should use. Could someone possiblely shed some light
on what I could possibly do to correct this issue? If you need more
details - I would be happy to provide them.

TIA!
Brian

There are a couple of things to note here. First up, you should not be
running a DC/DNS server as a router (except with SBS server which is built
to run that way). There are all sorts of problems which arise if you do.

The second is that, if you are running a domain, all machines should be
using the local DNS. To resolve foreign URLs, set this DNS to forward to a
public DNS service.

I would recommend that you reconfigure your network so that the DC has
only one NIC. Set all machines, including the DC to use the DSL router as
the gateway but use the DC for DNS. (ie manually set the DC to do this and
reconfigure DHCP so that the client machines do as well).



"Brian Patterson" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>I have a server 2003 machine that runs Exchange server. This server has 2
>network cards. [LAN] card is obviously connected to a network switch that
>all users in the office use (since the server is also the AD domain
>controller) and this network also has a cable modem on it. The WAN card in
>this machine connects to a network switch that is then connected to a DSL
>modem (and this card is the only one that has a gateway defined). The
>reason for this is that all email comes in through the static IP address of
>the DSL modem and when we send email - it goes out through the DSL line.
>
> Server 2003 is running a DHCP server that hands out IP address and sets
> everyones DNS to that of the server and their gateway to that of the cable
> modem that is on the LAN in the office. We prefer everyone in office use
> the cable modem and that the DSL line is only used for Email (in a
> nutshell). We have noticed that when users change their DNS not to use
> that of the server - their internet speed is really fast! *But* when we go
> with what DHCP hands out (using DNS on the server) everything runs really
> slow. I used performance monitor to check DNS and it is running fine. I
> then disconnected the DSL from the server and disabled that NIC and all
> the machines in the office started to move a lot faster.
>
> I concluded that I have some strange routing issue going on or something -
> because of the way I have the server set to use a different gateway that
> the clients in the office should use. Could someone possiblely shed some
> light on what I could possibly do to correct this issue? If you need more
> details - I would be happy to provide them.
>
> TIA!
> Brian
>

Actually the machine is SBS 2003. And I'm not actually using it as a
router - at least not that I'm aware of. It's main purpose is Exchange
Server, DNS and DHCP. The DHCP hands out IP addresses and the address of
the DNS server and address of the gateway. The gateway address it gives to
clients is that of the cable modem. The server itself actually accesses the
internet via the second NIC which is connected to a DSL modem.

All machines are currently pointed at the server for DNS and the server is
set to forward foreign URLS looksups to a outside server.

We don't really want everyone using the DSL because not only are we running
Exchange server over this DSL put we have a web server as well and all the
web traffic for this server comes in over the DSL. We want to ensure that
when employees are browsing the net, downloading files (or whatever) it
doesn't affect the response of the web server or mail server. Does this
make sense?

Unfortunately - since the server has 2 NICs seems to be an issue when
processing DNS. Like I said - if a user opens up their browser and types in
a URL - it literally takes 5 to 10 seconds for the page to start to display
and all the while the status bar of the browser indicates it is looking up
the site. Once the site starts to load it seems to go very fast but the
initial lookup just drags.... If we change the DNS on the client pc to
point to the cable modem rather than the DC - the client PC is blazingly
fast when browsing the web... It almost as if the client PC sends a DNS
request to the server. THe server looks up the information and then when it
attempts to respond - the response is sent to it's default gateway (DSL)
which doesn't work because the clients aren't on that network. After a
timeout or whatever - the in figures it out and sends the response to the
correct NIC and the reponse gets back to the client. Can that happen?

Thoughts?

"Bill Grant" <not.available@online> wrote in message
news:%(E-Mail Removed)...
> There are a couple of things to note here. First up, you should not be
> running a DC/DNS server as a router (except with SBS server which is built
> to run that way). There are all sorts of problems which arise if you do.
>
> The second is that, if you are running a domain, all machines should be
> using the local DNS. To resolve foreign URLs, set this DNS to forward to a
> public DNS service.
>
> I would recommend that you reconfigure your network so that the DC has
> only one NIC. Set all machines, including the DC to use the DSL router as
> the gateway but use the DC for DNS. (ie manually set the DC to do this and
> reconfigure DHCP so that the client machines do as well).
>
>
>
> "Brian Patterson" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>>I have a server 2003 machine that runs Exchange server. This server has 2
>>network cards. [LAN] card is obviously connected to a network switch that
>>all users in the office use (since the server is also the AD domain
>>controller) and this network also has a cable modem on it. The WAN card
>>in this machine connects to a network switch that is then connected to a
>>DSL modem (and this card is the only one that has a gateway defined). The
>>reason for this is that all email comes in through the static IP address
>>of the DSL modem and when we send email - it goes out through the DSL
>>line.
>>
>> Server 2003 is running a DHCP server that hands out IP address and sets
>> everyones DNS to that of the server and their gateway to that of the
>> cable modem that is on the LAN in the office. We prefer everyone in
>> office use the cable modem and that the DSL line is only used for Email
>> (in a nutshell). We have noticed that when users change their DNS not to
>> use that of the server - their internet speed is really fast! *But* when
>> we go with what DHCP hands out (using DNS on the server) everything runs
>> really slow. I used performance monitor to check DNS and it is running
>> fine. I then disconnected the DSL from the server and disabled that NIC
>> and all the machines in the office started to move a lot faster.
>>
>> I concluded that I have some strange routing issue going on or
>> something - because of the way I have the server set to use a different
>> gateway that the clients in the office should use. Could someone
>> possiblely shed some light on what I could possibly do to correct this
>> issue? If you need more details - I would be happy to provide them.
>>
>> TIA!
>> Brian
>>
>

"Brian Patterson" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>>
> We don't really want everyone using the DSL because not only are we
> running Exchange server over this DSL put we have a web server as well and
> all the web traffic for this server comes in over the DSL. We want to
> ensure that when employees are browsing the net, downloading files (or
> whatever) it doesn't affect the response of the web server or mail server.
> Does this make sense?

To be frank, no it doesn't make any sense to me. There is really no
practical way to use more than one Internet connection on a single LAN. Even
if your DC is not routing it is multihomed, and that is always a problem.
>
>> "Bill Grant" <not.available@online> wrote in message
> news:%(E-Mail Removed)...
>> There are a couple of things to note here. First up, you should not be
>> running a DC/DNS server as a router (except with SBS server which is
>> built to run that way). There are all sorts of problems which arise if
>> you do.
>>
>> The second is that, if you are running a domain, all machines should
>> be using the local DNS. To resolve foreign URLs, set this DNS to forward
>> to a public DNS service.
>>
>> I would recommend that you reconfigure your network so that the DC has
>> only one NIC. Set all machines, including the DC to use the DSL router as
>> the gateway but use the DC for DNS. (ie manually set the DC to do this
>> and reconfigure DHCP so that the client machines do as well).
>>
>>
>>
>> "Brian Patterson" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed)...
>>>I have a server 2003 machine that runs Exchange server. This server has
>>>2 network cards. [LAN] card is obviously connected to a network switch
>>>that all users in the office use (since the server is also the AD domain
>>>controller) and this network also has a cable modem on it. The WAN card
>>>in this machine connects to a network switch that is then connected to a
>>>DSL modem (and this card is the only one that has a gateway defined).
>>>The reason for this is that all email comes in through the static IP
>>>address of the DSL modem and when we send email - it goes out through the
>>>DSL line.
>>>
>>> Server 2003 is running a DHCP server that hands out IP address and sets
>>> everyones DNS to that of the server and their gateway to that of the
>>> cable modem that is on the LAN in the office. We prefer everyone in
>>> office use the cable modem and that the DSL line is only used for Email
>>> (in a nutshell). We have noticed that when users change their DNS not
>>> to use that of the server - their internet speed is really fast! *But*
>>> when we go with what DHCP hands out (using DNS on the server) everything
>>> runs really slow. I used performance monitor to check DNS and it is
>>> running fine. I then disconnected the DSL from the server and disabled
>>> that NIC and all the machines in the office started to move a lot
>>> faster.
>>>
>>> I concluded that I have some strange routing issue going on or
>>> something - because of the way I have the server set to use a different
>>> gateway that the clients in the office should use. Could someone
>>> possiblely shed some light on what I could possibly do to correct this
>>> issue? If you need more details - I would be happy to provide them.
>>>
>>> TIA!
>>> Brian
>>>
>>
>
>

"Brian Patterson" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>I have a server 2003 machine that runs Exchange server. This server has 2
>network cards. [LAN] card is obviously connected to a network switch that
>all users in the office use (since the server is also the AD domain
>controller) and this network also has a cable modem on it. The WAN card in
>this machine connects to a network switch that is then connected to a DSL
>modem (and this card is the only one that has a gateway defined). The
>reason for this is that all email comes in through the static IP address of
>the DSL modem and when we send email - it goes out through the DSL line.

Why the desire to have two separate internet connectsion (cable & DSL)? If
you want to ensure bandwidth for browsing or smtp then I would suggest
getting a router that provides quality-of-service (QoS) so you can
prioritise different types of traffic.

> Server 2003 is running a DHCP server that hands out IP address and sets
> everyones DNS to that of the server and their gateway to that of the cable
> modem that is on the LAN in the office. We prefer everyone in office use
> the cable modem and that the DSL line is only used for Email (in a
> nutshell). We have noticed that when users change their DNS not to use
> that of the server - their internet speed is really fast! *But* when we go
> with what DHCP hands out (using DNS on the server) everything runs really
> slow. I used performance monitor to check DNS and it is running fine. I
> then disconnected the DSL from the server and disabled that NIC and all
> the machines in the office started to move a lot faster.

Your problem almost certainly lies at the server. I assume that it is slow
to resolve dns names.

Which connection does the server use when it resolves dns requests? I assume
your ISP(s) have provided different DNS servers for each connection? Get
them the wrong way round and I'm sure it would impact performance.

If your server only knows about the DSL line then check that the ISP's DNS
servers are correctly configured. It might also be worth comparing the speed
of the DNS servers for both of your ISPs.

> I concluded that I have some strange routing issue going on or something -
> because of the way I have the server set to use a different gateway that
> the clients in the office should use. Could someone possiblely shed some
> light on what I could possibly do to correct this issue? If you need more
> details - I would be happy to provide them.

Whilst I don't see why it shouldn't work in principle, I agree with Bill
that its probably wise to move away from the multi-homed configuration.
--
Brian Cryer
www.cryer.co.uk/brian