What makes an Ethernet/IP (CIP) message send or skip a List Services request?

CIP
ENET
list
services

asked 2021-01-08 13:53:09 +0000

wshvw
1

Hi,

One of our slave PLC's types is not able to send a correct Ethernet/IP (CIP) message as the master does not respond. The master responds correct to other slave PLC types. In wireshark we can see that with the passing communication the slave sends a (ENIP) List Services request prior to sending a Register Session request and then sending data. The failing PLC type skips the (ENIP) List Services request before sending the Register Session request and the master will not respond.