Windows 7 Networking Multiple NICs

Posted on 2012-08-17
Last Modified: 2012-08-26
I have a Windows 7 Pro machine with 3 NICs.  One is the main network NIC and has worked fine for some time.  The other two are wired to managed switch monitoring ports using random, off subnet, ip addresses .. since they only need to receive.  Then I can look at them with Wireshark.
(I don't want the monitor traffic on the main subnet of course).
This has worked very well.
Suddenly I can't see any of the computers on the network.
now if I use net view, I get the "can't be found or opened" message.

So I changed the node type to broadcast or "1" in the registry.

Now net view shows my computer as the Master Browser.  But it's on one of the monitor NIC IP addresses!!  ??

So, I disabled the monitor NICs and now I can see the computers on the network.  
But I don't want them disabled.

I don't understand what happened to cause this.  I'd like to understand.
If there's a better way to do monitoring, I'd like to know.
Question by:Fred Marshall
    LVL 10

    Expert Comment

    try putting fixed IP on all your NIC and run pings from various points of your network.
    this would test - connectivity, see if the problems in in your IP leasing, NIC

    ping from one NIC to the other onthe same machine.

    is you firewall blocking your IP or NIC? SEP has a feature to that that...

    i think that its your local firewall
    LVL 25

    Author Comment

    by:Fred Marshall
    All of the IP addresses are static.
    The main LAN subnet is  The main NIC for this computer uses
    The other two NICs use and and only connect to the switch mirror ports.

    The issue is with the main NIC seeing other computers on the LAN subnet.
    LVL 25

    Author Comment

    by:Fred Marshall
    It occurs to me that there is no way for the OS to know which is the "main" NIC for the LAN except that the two "monitor" NICs don't have a gateway entry.

    Is that all or is there some other way to distinguish for things like Master Browser election, etc?
    LVL 20

    Accepted Solution

    Enable the monitoring cards but disable all bindings on them. Winpcap driver used in Wireshark and any other capturing tool don't make use of the services enabled on the cards, including its IP address. However, the card must support promiscuous mode in order to receive all packets from the switch monitoring ports.

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