Hirschman RS20 with 15 1794-AENT modules


Thread Starter

Jerry Flynn

Trying to upgrade my I/O with a managed hirschman RS20E switch, I've been through AB's whitepaper. I've got 2 Hirschmans working fine but with less traffic going to ENBT modules now but when I try to connect the 3rd my modules go on and offline like crazy. I've got IGMP snooping enabled, I've tried increasing my timeslice, been through MANY hirschman settings. I'm communicating to a Control Logix processor, initailly communication is fine but then I start losing the modules. I'm not showing any collisions or CRC errors in the Hirschman statistics either...can anybody help???

Bob Peterson

there are known bugs in some versions of hirschman switches when used this

get the latest firmware for the switch.

Nathan Boeger

Some ideas that come to mind for troubleshooting:

Is that a layer 2 or 3 managed switch?
Have you looked into the firmware?
Have you tried configuring it like one of the 2 that work and swapping it?
You might plug in a computer with the ethernet adapter in promiscuous mode running a packet sniffer.
How long are your cable drops and are the ends done correctly?
Do you have any VLANs set up? You might try using VLANs, or more simply, plug in and set up a subset of your network. You may be on to something suspecting multicast timeouts with IGMP. VLANs will go a long way to help with broadcast storms and you will still be able to use routes with the friendlier, connection oriented comms.

Most importantly, do what you can to eliminate variables - this is just like PLC troubleshooting. Wire and configure a few nodes with known good, short cables. Observe all that's going on as you add to the configuration. You don't need to be a networking guru to spot symptoms.

Nathan Boeger
"Design Simplicity Cures Engineered Complexity"