We have a CISCO 3640 software version 12.3 with a 16 port 16am analogue modem module. We have a scada system which connects to each of these modems via a telnet session to the port.

The problem we have occurs when there is a network failure/glitch between the scada server( remote site)or (local site) and the router. The telnet sessions are not dropped by the routers and when the scada system tries to connect back in it sees them as unavailable because the router still thinks it has connections. I have implemented a exec-timout 240 0 so it should restart and clear the lines every 4 hours. I dont think it can be done on idle data time as the modems are sometimes not used for long periods but the scada still needs a connection open to them incase. Any suggestions ??