Re: MultiHomed Workstation - Which NIC is being used?

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From: RDK (RDK_News_at_NoSpamHotMail.com)
Date: 01/13/05 

Date: Wed, 12 Jan 2005 19:42:02 -0500

Steve.....Hmmmmm. If the inbound traffic is sent to the internet address
for NIC2, is processed by my workstation, and the response is sent back via
NIC1 and its different Internet IP address won't that cause the originating
firewall to reject the reply?....RDK

"Steve Riley [MSFT]" <steriley@microsoft.com> wrote in message
news:47649632411418526460683@news.microsoft.com...
> Reply traffic follows whichever route it has to, according to the source
> addresses of the inbound traffic. Regardless of which interface received
> the inbound traffic, the same routing rules apply for return traffic. So
> if it comes in on NIC2 but NIC1 is able to route back to the source, your
> computer will use NIC1 to send the reply so long as that NIC is bound
> highest.
>
> Windows (like nearly all operating systems) follows what's called the
> "weak end-system" model where there is no real link kept between
> interfaces and flows. It's all up to the routing engine to decide where to
> send traffic, and that decision is made on a per-packet basis.
>
> Steve Riley
> steriley@microsoft.com
>
>
>
>> Steve.....Thanks this answers almost all of my questions. However,
>> recalling my PS and your #4 below:
>>
>> 4. All other traffic will leave the adapter that's highest bound.
>>
>> 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?...
>> Let's assume that NIC1 is the "highest bound", does this mean that
>> traffic from the 10.0.1.* subnet (coming in via NIC2) to a web server
>> on my workstation from an Internet source (firewall DMZ for example)
>> will exit back to the Internet via NIC1, or will it know that it has
>> to exit via NIC2?
>>
>> Thanks......RDK

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