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How to Scan for TCP/IP Instruments Through a Specific Ethernet Port

Primary Software: Utility Software>>Measurement & Automation Explorer
Primary Software Version: 3.1
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem: I have a computer with dual Ethernet boards. When I go to Measurement and Automation Explorer (MAX) and scan for TCP/IP Instruments it takes a long time because it is scanning through both ports. How can I make the scan only be through one of my ports?

Solution: MAX has no way to define which port or NIC to use if it doesn't know the IP address of the instrument, so it will try to scan through both networks.
One good solution is to specify a static route in the computer to route that scan through a specific card.

When MAX does a scan for TCP/IP instruments like VXI 11 instruments, it sends a broadcast to the whole network. It will send a packet to the address 255.255.255.255.

That said, what you need to do is modify the routing table that the computer uses.

  • Open a CMD or DOS window and type route.

  • That will give you all the help for that function.

  • To see what routes have been declared, type route print.

  • You will see at least one route to an IP address 255.255.255.255 with the same mask, where the gateway is the IP address of the Ethernet ports.

  • When you have two Ethernet ports you will have two routes like this, one for each port.

  • The only thing we need to do is to modify the METRIC of the one that we would not like to use to have a higher value than the other route.

  • That will make broadcasts go through one port in specific.

Be aware that doing this will make all broadcasts go through a specific port so it will also affect any other software that needs to send a broadcast.


Related Links:
KnowledgeBase 2CMST8V: How Do I Control Ethernet Instruments with NI-VISA?
KnowledgeBase 2YIFKEN1: How Do I Configure an Instrument to Communicate via TCP/IP in MAX?

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Report Date: 10/07/2004
Last Updated: 10/07/2005
Document ID: 3E6CRNRY

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