Re: MultiHomed Workstation - Which NIC is being used?

From: RDK (RDK_News_at_NoSpamHotMail.com)
Date: 01/12/05 

Date: Tue, 11 Jan 2005 19:12:12 -0500

Steve...Thanks for the information, except now I'm a bit confused by the
reference article you sent me to. May I elaborate on my setup:

    NIC1 10.0.0.5 has a gateway (firewall router address) of 10.0.0.1 and
its "modem" is connected to ISP1 - 5 MBS
    NIC2 10.0.1.5 has a gateway (firewall router address) of 10.0.1.1 and
its "modem" is connected to ISP2 - 1 MBS
    NIC3 10.0.2.5 has a gateway (firewall router address) of 10.0.2.1 and
its "modem" is connected to ISP3 - 0.25 MBS
except via my workstation these three subnets are not connected (well I
guess they are connected via the Internet).

In this mode if I fire up an app on my Win2k workstation which wants to
access the interent, I'm never sure which NIC is actually servicing the
request. In a development and production environment I prefer to keep the 5
MBS pipe clear for business traffic and use one of the others for testing.
But, I do need to access devices on the 5 MBS subnet periodically. Now, my
read of the reference article is that I should leave the gateway field blank
for NIC's 1 and 3, and to populate NIC2 with all three router addresses. Is
this correct? And then I have to use the Router.exe to define routes for
the other two??

Networking is not my speciality, can you provide a couple concrete examples.

Thanks....RDK

ps...I assume that any incoming traffic to my workstation webs and/or
databases from devices (servers and/or users) on any of the three subnets
will always return via the NIC on which it was received?...

"Steve Riley [MSFT]" <steriley@microsoft.com> wrote in message
news:45224632410457423941917@news.microsoft.com...
> The Windows IP stack supports only one default gateway. If all three of
> your interfaces have routes out to the Internet, you will be using only
> one interface. Which interface gets used depends on how you've configured
> the stack.
>
> In no instance will you get any form of traffic load balancing. You can
> configure varying metrics, but that usually makes sense only if you're
> trying to make routing decisions based on cost. If you use a lower (that
> is, more preferred) metric for faster connections then *all* your traffic
> will go out that connection. If you use the same metric everywhere,
> Windows XP and 2003 will use only one interface for all traffic -- the one
> that's listed first in the binding order in the advanced settings dialog.
> Windows 2000 just randomly picks one.
>
> See http://support.microsoft.com/?id=157025 for some more details on your
> configuration.
>
> It sounds like you're describing a need for "ISP load balancing."
> Rainfinity makes a product called RainConnect that does exactly that.
> Check it out.
>
> Steve Riley
> steriley@microsoft.com
>
>
>
>> You could do it 2 ways and still achieve the same result.
>>
>> In the Advanced properties of your network connections set a metric
>> for each connection, a lower metric set to an interface makes that
>> connection a preferred route for all outgoing traffic. Setting
>> multiple interfaces with the same metric enables load sharing across
>> these connections.
>>
>> If you are looking to set an application process (iexplore.exe in
>> your case) to use a connection-of-choice for that process all the
>> time, i don't think there is a way (but i am willing to be wrong about
>> this).
>>
>> The next method used the Route.exe command line executable to set the
>> metric for gateways using a default route which is persistent across
>> system reboots.
>>
>> % Route Add 0.0.0.0 Mask 0.0.0.0 10.0.2.5 Metric 20 -p Let's say this
>> was your 5MB connection
>>
>> % Route Add 0.0.0.0 Mask 0.0.0.0 10.0.1.5 Metric 22 -p and this was
>> your 2MB connection
>>
>> % Route Add 0.0.0.0 Mask 0.0.0.0 10.0.0.5 Metric 35 -p and this was
>> your 0.25MB connection
>>
>> RDK wrote:
>>
>>> ....I have a Windows 2000 workstation which has three NICs. Each NIC
>>> (subnets 10.0.2.5, 10.0.1.5 and 10.0.0.5) has an independent route to
>>> the internet. That is we have three redundant routes to the internet
>>> (three different suppliers).
>>>
>>> One of these routes is low speed (250 KBS) while the others are 1MB
>>> and 5MB.
>>>
>>> How can I tell which NIC is being used when I open up IE? Or, how
>>> can I specify (without disabling the other NICs) which NIC should be
>>> the primary (preferred) NIC, secondary, ... for internet access?
>>>
>>> Thanks....RDK
>>>
>
>

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