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Communication Problems with Ethernet
We have seen a problem with Ethernet communication to the PMAC from specific computers. The problem usually happens when user wants to use the Plot or Tuning program.

Most of the time the problem happens if you have installed any sort of VPN software (specially Cisco VPN) on your machine, which will add a MTU setting in Windows registry causing the packet size to be limited to 1400 or so many bytes, which causes the communication failure to the PMAC since the packets will be chopped off.

You can fix this problem by removing the MTU settings from the registry.
Here is the location to look for the MTU key:


under each Key, there may be a MTU entry, which you have to delete.

Sina Sattari
Hardware Engineering Manager
Delta Tau Data Systems, Inc.
These are also possible causes for communication problems with Ethernet:

In Pewin32Pro/Pewin32Pro2 Ethernet mode of communication users sometime experience data loss. There are two possible reasons for that:

1 . MTU is set to a number less than 1492. Solution: You need to locate and remove MTU entry or increase its value in registry to 1500 for all Ethernet Interfaces. MTU entry (if any) is located in the following registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces

2. In the Network connections another protocol known as “Deterministic Network enhancer” is enabled. Solution: Remove this protocol from the properties of Network Interface Card which will communicate to PMAC.


a. After the above steps, restart Network Interface Cards. And restart Pewin32Pro2 or other Delta Tau application.

b. If in the previous session Pewin32Pro2 dropped any data packet then you must restart PMAC as well.
Sina Sattari
Hardware Engineering Manager
Delta Tau Data Systems, Inc.

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