1769-L23ER-B1BB Ethernet Problems

Hello all,

We have an implementation where our custom software and driver reads/writes configuration data from/to the PLC into normal tags. Some of these locations are remote so we use a cellular ethernet modem to connect remotely from administration. It seems that the communications drop out from time to time when we are performing a "sync". This dropout appears to be "holding" the port open on the PLC.

We hit the WAN IP address and establish our connection to the cell modem and everything appears to be working fine, port forwards are all intact. When we cycle power on the PLC everything comes back up.

Are there known firmware issues? Better yet, is there a way to perform a reboot of the PLC or the ethernet daughterboard with an internal tag? I could detect comm failure and reboot if there is no use at the station.

Thanks!

There's almost certainly going to need to be some network analysis done.

Have you been able to quantify or capture the failure ?

How frequently is "from time to time" ?

Can you describe exactly what you mean by "hold the port open" ?

Is the controller exchanging TCP Keepalives with the cellular gateway ?

Does the condition ever remedy itself without intervention ?

My guesses align with yours; I suspect the cellular gateway is keeping the TCP connection alive on the LAN side even when it's closed or timed out or broken on the WAN side.

RA doesn't have a "reboot PLC" bit except for an intentional fault, and I wouldn't do that. You could conceivably also send a Reset service to the Ethernet daughtercard.

I can't see this being a bug on the controller's side; as far as it knows it has a TCP connection and as long as that device is responding to Keepalives, it's going to keep that TCP connection up.

A Wireshark capture on the LAN side would be terrific for this.