MAC addresses used in EtherCAT frames

[radar_macgyver]

What is the source and destination MAC address used for frames sent on an EtherCAT link? I could see that the source address is that of the master, but since there can be multiple nodes and the same packet traverses each one, what would the destination address be?

[radiolistener]

It seems that there is no free and open documentation.
But at a glance it uses UDP packets or ethernet packets with etherType=0x88A4 as envelope.
So it seems that it uses usual MAC addresses, the same as usual ethernet. Probably with the same ARP.

[fchk]

If you use direct mode (Master - slave1 - slave2 - slave3 ...), then the mac addresses aren't checked.

If you use open mode (Master - Switch - n slave chains), then the destination MAC is the MAC of the first slave of the chain being addressed.

Reference: ETG1000.3 Section 4.7.2

And no, UDP is not used. These are special Ethercat frames.

[radiolistener]

And no, UDP is not used. These are special Ethercat frames.

[jbb]

It’s been a while, but I seem to recall something about ‘proper’ - I.e. no Ethernet switch - EtherCAT setups being able to all use the same MAC address

[radiolistener]

It’s been a while, but I seem to recall something about ‘proper’ - I.e. no Ethernet switch - EtherCAT setups being able to all use the same MAC address

Does it means that it just ignore eth.src and eth.dst? Such implementations definitely will not work on any medium, as promised...