Ethernet/IP connection fault
- Thread starter CroCop
- Start date
Ken Roach
Lifetime Supporting Member + Moderator
You have all kinds of interesting stuff on this network. Acromag, Moxa, ProLinx, A-B... There's a switch with a webpage interface that I can see, with a Java applet showing you statistics.
I see Acromag devices on subnet 192.168.144.x at IP addresses .81,82,83,84,94,95,96,98,99,101, and 102. Did I miss any ?
The first capture shows traffic mostly between .31 (the 1756-ENBT) and .81 (one of the Acromag units).
The second capture shows mostly the data originating from the 1756-ENBT to many nodes but not the reply data and the data replies are mostly not being seen. This might have been taken from an incorrectly configured mirror port or a switch.
I see Acromag devices on subnet 192.168.144.x at IP addresses .81,82,83,84,94,95,96,98,99,101, and 102. Did I miss any ?
The first capture shows traffic mostly between .31 (the 1756-ENBT) and .81 (one of the Acromag units).
The second capture shows mostly the data originating from the 1756-ENBT to many nodes but not the reply data and the data replies are mostly not being seen. This might have been taken from an incorrectly configured mirror port or a switch.
Yep. Moxa switch uses a Java interface to get show stats.
The first capture shows traffic on a unit that I've had fault quite a bit, but I didn't see anything out of the ordinary.
The second unit I had the mirror port set incorrectly, or there is never any data coming back. I'll grab a hub & do it the simplest way possible.
Was there anything that you saw that stood out?
The first capture shows traffic on a unit that I've had fault quite a bit, but I didn't see anything out of the ordinary.
The second unit I had the mirror port set incorrectly, or there is never any data coming back. I'll grab a hub & do it the simplest way possible.
Was there anything that you saw that stood out?
Ken Roach
Lifetime Supporting Member + Moderator
Open up the Traffic2 file in the first capture you posted and look at the traffic around Frame 458.
Ordinarily there's one packet from the -ENBT at address .31, and another packet from the Acromag at address .81.
Around Frame 458, each device starts to have to retry once, because it didn't hear a corresponding packet from the other device. The retries are 50 ms apart and usually there's only one retry.
I think that this indicates that somewhere in the lower level of the network there is something keeping packets from being correctly transported from .31 to .81 and vice versa. It might be a loose plug, or a bottleneck in a switch... it's hard to say.
When a device retries, it increments the sequence number. If the other device doesn't retry, you get a difference in sequence numbers. If both devices retry the same number of times, the sequence numbers also don't get out of step.
You can see in that capture file that the sequence numbers of adjacent packets are out of step; by the time you get to Frame 1000 of this capture, the values are 961531 from .31 and 956395 from .81.
This means that the 1756-ENBT at .31 has retried about 5100 times more than the Acromag has. I think this means that the Acromag is more often not replying (or the reply is not being heard) than vice versa.
Disconnect the Acromag and the sequence numbers will go to zero. That will let you establish what the average unbalanced retry rate is over a period of time.
Ordinarily there's one packet from the -ENBT at address .31, and another packet from the Acromag at address .81.
Around Frame 458, each device starts to have to retry once, because it didn't hear a corresponding packet from the other device. The retries are 50 ms apart and usually there's only one retry.
I think that this indicates that somewhere in the lower level of the network there is something keeping packets from being correctly transported from .31 to .81 and vice versa. It might be a loose plug, or a bottleneck in a switch... it's hard to say.
When a device retries, it increments the sequence number. If the other device doesn't retry, you get a difference in sequence numbers. If both devices retry the same number of times, the sequence numbers also don't get out of step.
You can see in that capture file that the sequence numbers of adjacent packets are out of step; by the time you get to Frame 1000 of this capture, the values are 961531 from .31 and 956395 from .81.
This means that the 1756-ENBT at .31 has retried about 5100 times more than the Acromag has. I think this means that the Acromag is more often not replying (or the reply is not being heard) than vice versa.
Disconnect the Acromag and the sequence numbers will go to zero. That will let you establish what the average unbalanced retry rate is over a period of time.
With more Ethereal Traces, I think I got to the bottom of this.
I had a device (Moxa EDS-308 Switch) Querying on IGMP. It was flooding the Network with Broadcasts, so I turned the Querier off. I beleive this is it, when I'm sure, I'll hit it back.
I had a device (Moxa EDS-308 Switch) Querying on IGMP. It was flooding the Network with Broadcasts, so I turned the Querier off. I beleive this is it, when I'm sure, I'll hit it back.
TimWilborne
Lifetime Supporting Member
Just wanted to say thanks for the excellent lesson Ken. I have played with Ethereal and have used it to poke around a network, but I think this thread has given me a firmer grasp on what exactly I should be looking for
CroCop said:
Turns out "this morning" turned into "this afternoon". Funny how that happens.......
Anyhow,
I've had a major fault, and the ip addys in question are .31 & .111.
They are both Rockwell Devices, a 1756-ENBT & a 22-COMM-E. I can ping both, I can see both on the network using Look@Lan.
Problem is, the 2 devices don't see eachother.
I've attached a Ethereal Trace, one from the Controller Side, the other from the IO Side. Put ip.src == 192.168.144.111 or ip.dst == 192.168.144.111 in the Filter, Click Apply, & see what's going on.
I'd sure like it if Ken saw this & weighed in.
ricardo06
Member
hello i need information about how do it ethernet conection between plcs allend bradlley
ricardo06
Member
I am student i need to know how do it etnernet conexion between plsc
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