I'm monitoring several devices (RB411U + 3G modem) using dyndns service.
Due I could have wrong DNS-IP assignment, I'll check RB411 on http port (port 8292 instead 80) with probe on TCP, port 8292, connect-only.
In this way I can check something behind RB411U public IP (like devices on private lan), for example on port 23 (telnet) using probe TCP port 8293, connect only (of course, I make NAT on RB411U).
Looking probe graphs, I can often see a lot of blank spaces, so I suppose I could have DNS not updated.
So I made a script on RB411U sending to ftp server logs about IP addresses: both resolved DNS and public IP address (got from monip website).
Sometimes 3G modem doesn't work, in this case TCP re-probe (on port 8292) could look immediately okay, but ping goes to timeout.
Now, ping must go to timeout because RB is not connected to internet, but how TCP probe is "OK"??????
In remaining cases, TCP probe doesn't work, but log files (where there are contained both public IP taken from "3G" interface and public IP taken from "monip" website) says public IP address has not been changed.
Both probes are set on 5m interval and 15s timeout.
What's could be wrong?