CHAPTER 3Configuring the Gateway112Secondary ServerFigure 109. SSH Tunnel - Secondary ServerA secondary SSH server can be used as alternative SSH tunnel, e.g.if no connection to the primary SSH service can be established. Analternative SSH service with identical or different host name can beused for the secondary SSH server.Note: In principle, a secondary SSH server is not necessary for aSSH tunneling.Notification SendingA notification is an event that is either created by a sensor of anRTU changing its value (digital ports) or reaching a configuredthreshold (analog ports), an RTU itself (depending on data delayand radio error rates) or the Gateway (for some internal events likerebooting, configuration changes, dialling into an ISP). These noti-fications are queued and sent to the notification server.The A850 supports sending notifications to servers using HTTP,SMS and SMTP (E-Mail) over a primary and a secondary server foreach of these methods. The primary server is tried first, the sec-ondary only when the primary server couldn't be contacted.Note: To send notifications as SMS messages, an external GSMmodem must be connected to the A850!
