Re: EtherCAT can't be captured though Ethernet works

[Guy Harris <guy () alum mit edu>]

On Jun 10, 2011, at 6:27 AM, N Nguyen wrote:

> I am using EtherCAT, and I'd like to use wireshark to capture the frames.
> If I stop the EtherCAT, the eth0 is listed in the capture list, and everything is OK.
> But if I start EtherCAT, the ifconfig tells that there's only local loopback lo 127.0.0.1. And apparently wireshark 
> cannot capture the EtherCAT, although I am transferring frames via my NIC card (RTL 8139).

What do you mean by "stop the EtherCAT" and "start the EtherCAT"?  Is this something you do on the machine running 
Wireshark, or just on the network?  If it's something you do on the machine running Wireshark, perhaps the EtherCAT 
implementation somehow turns the Ethernet adapter into something that the rest of the networking stack doesn't 
recognize as a network interface, so that the rest of the networking stack - including the packet capture mechanism - 
can't use it.

(I'm guessing, from "local loopback lo 127.0.0.1", that you're running on Linux, where the loopback interface is 
generally called just "lo", rather than "lo0".  What does "ifconfig -a" report when EtherCAT has been started and when 
EtherCAT has been stopped?)
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