1) Yes, you can dial the EX90 with the Web interface, or with the CLI (via Telnet or SSH).
2) The devices generally don't just lose connectivity - there may be an issue with the configuration on the device where it is now on a different IP address than you expected. For the best troubleshooting, I'd suggest you connect to it via the serial port and look at the configuration via that (note: it's not a standard serial port and you will need to make an adaptor).
Wayne
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