Hi everyone,
I've experienced a very unusual problem and searching I came across this forum and thought I'd give it a shot.
I am not a PLC specialist, my business is industrial ethernet networks. The problem came up at a particular plant where I was replacing a 3com office line (superstack) switch with a Hirschmann MICE industrial switch.
Basically it is a very small network, consisting of 4 PLCs (2x Control Logix + 2x SLC) and 3 workstations. What is usually a very smooth changeover had a serious glitch today - one of the PLCs could not be PINGed or picked up by RSLinx. The weird thing is that the SNMP software for the Hirschmann switch was showing the correct MAC address connected to the port on the switch, and the activity light was on, so there definitely IS a connection. After fiddling with the speed and duplex settings, and nothing having any effect, I did the following: plugged the offending PLC to the 3com switch, and then the 3com switch into the Hirschmann switch - now I could ping it, RSLinx could see it and everything was OK.
Then, I got the PLC guy to prepare a new ENET module with the particular IP address, to eliminate any problems with the module. He did, and as he plugged it into the backplane, same situation - I could see its MAC on the port on the Hirschmann switch, activity light was on, BUT this time I could PING it!!! Unfortunately, still no joy with the RSLinx.
I had to leave with the sad state of affairs, having plugged the PLC into the 3com and then the 3com into the Hirschmann switch - thus negating the purpose of the whole changeover.
I have done this numerous times with exact same PLCs and never had this problem. The other PLC on the same network was instantly recgonised and picked up by RSLinx. I compared the settings of the two ENET modules and there was no difference (apart from the IP addresses of course).
I am really baffled, can someone help or point me to a resource where I could read up on what may be causing this?
Thanks,
Vlad.
I've experienced a very unusual problem and searching I came across this forum and thought I'd give it a shot.
I am not a PLC specialist, my business is industrial ethernet networks. The problem came up at a particular plant where I was replacing a 3com office line (superstack) switch with a Hirschmann MICE industrial switch.
Basically it is a very small network, consisting of 4 PLCs (2x Control Logix + 2x SLC) and 3 workstations. What is usually a very smooth changeover had a serious glitch today - one of the PLCs could not be PINGed or picked up by RSLinx. The weird thing is that the SNMP software for the Hirschmann switch was showing the correct MAC address connected to the port on the switch, and the activity light was on, so there definitely IS a connection. After fiddling with the speed and duplex settings, and nothing having any effect, I did the following: plugged the offending PLC to the 3com switch, and then the 3com switch into the Hirschmann switch - now I could ping it, RSLinx could see it and everything was OK.
Then, I got the PLC guy to prepare a new ENET module with the particular IP address, to eliminate any problems with the module. He did, and as he plugged it into the backplane, same situation - I could see its MAC on the port on the Hirschmann switch, activity light was on, BUT this time I could PING it!!! Unfortunately, still no joy with the RSLinx.
I had to leave with the sad state of affairs, having plugged the PLC into the 3com and then the 3com into the Hirschmann switch - thus negating the purpose of the whole changeover.
I have done this numerous times with exact same PLCs and never had this problem. The other PLC on the same network was instantly recgonised and picked up by RSLinx. I compared the settings of the two ENET modules and there was no difference (apart from the IP addresses of course).
I am really baffled, can someone help or point me to a resource where I could read up on what may be causing this?
Thanks,
Vlad.