Think & Do Frequently Asked Questions
Question
I have 2 or more network cards installed in a computer where both are using TCP/IP protocol. I can PING the WinPLC, but cannot connect using ESP.
Answer
When 2 or more network cards are installed in a computer, this is referred to as a "multi-homed" system.The protocol manager needs to know which network card to send the TCP/IP packets over, and the WinPLC needs to know which one to respond to. This presents a requirement known as "IP Forwarding".
There are (2) requirements for resolving this issue.
For Windows NT:
Go to Control Panel->Networks->Protocols, and choose TCP/IP. Then click on the Properties button, and a dialog shall appear. Click on the tab labelled "Routing", and place a check mark next to "Enable IP Forwarding", then choose OK. Choose OK again to close the Network properties dialog, and reboot as instructed by the Windows NT.
For Windows 2000:
WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.
For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).
- Steps:
- Click on Start->Run, and type 'regedit' and press ENTER
- Navigate to the key [HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParameters]
- Find the value "IPEnableRouter", and double click on it
You will now get an opportunity to change it's value. Change it to '1' (without the quotes) to enable IP Forwarding.
- Reboot the machine to refresh the registry cache.
FAQ Subcategory: Communications
This item was last updated on 2013-09-26
Document ID: 893
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