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have two devices that communicate over Ethernet/IP - cannot get them conncted so found a Hub and connected them and my PC running Wireshark - what I see is the Client ( device making a connection to the Server device ( but then the Client goes to following: IGMP V2 Membership Report Join group

when it should simply continue talking to the Server device - consequently the connection between my devices' fails

Can anyone help me understand where this could come from

asked 17 Mar '11, 18:12

tonyh110's gravatar image

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retagged 18 Mar '11, 09:52

packethunter's gravatar image


I'm not familiar with Ethernet/IP (by which I'm assuming you mean Industrial Protocol) so I'll just note the following:

IGMP is a protocol in it's own right completely separate from TCP (which is presumably the protocol being used in "making a connection").

The IGMP message is merely the client requesting to receive multicast messages from group so I suspect "consequently the connection between my devices' fails" is not really correct.

What do you mean by "cannot get them connected" ? Does the TCP 3-way handshake complete ?

(17 Mar '11, 19:28) Bill Meier ♦♦

Bill, thanks for your reply - yes its industrial CAN bus over TCP/IP - once the Client device makes a connection then a CIP CM transaction opens - because the Client starts this IGMP request the Server device stops responding at the CIP level I have the Client device vendor working on the problem - but your answer helps me understand this much better - thing is Industrial Networks are deterministic and wont suffer timeouts (which begs why do they put such critical stuff through a non-deterministic transport layer)

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answered 18 Mar '11, 07:43

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question asked: 17 Mar '11, 18:12

question was seen: 4,833 times

last updated: 18 Mar '11, 09:52

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