TCL

Often IPv6 is used via dialup line and/or tunnel brookers. Sometimes the dialup fails, the tunnel is unavailable or not connected properly. With monitoring remote systems, it makes sense not only to check if the system is up and running, but also, in case of an error, to check if the connection from the monitoring system to the monitored system is valid.

To accomplish this, you can se a “parent” to the monitored system, and use a “gateway” as parent. The gateway is not checked directly, that means it is out of interest if the gateway is up and running (ping-able). Instead, the proper function of the gateway is checked. And this function is: “connect me to the internet”. In case this function is given, you can tell that a remote host which is not up has a problem, and not your internet/IPv6 connection.

Sometimes it would be nice to run two network services on the same tcp/ip port. The best example is ssh/https:

• https is available on most proxy servers, while ssh (port 22) is not
• if ssh could run in parallel with the web server, the https section would not need to be disabled.

To acomplish this, there is a small TCL script that does the following: