By clicking on an IP Address in the server status page, you can check if the destination server or phone is reachable via TCP/IP. This is done by sending an IP Ping (ICMP Echo Request) and waiting for the results. After a couple of seconds you will see the ping results similar to the following:
64 bytes from 184.108.40.206: icmp_seq=1 ttl=56 time=22.5 ms
64 bytes from 220.127.116.11: icmp_seq=2 ttl=56 time=23.0 ms
64 bytes from 18.104.22.168: icmp_seq=3 ttl=56 time=23.6 ms
64 bytes from 22.214.171.124: icmp_seq=4 ttl=56 time=23.4 ms
In the example above, four IP ping packats have been sent, and all four were answered after about 23 ms each. If there is no answer, you can assume that either the destination host has ceased working or that it cannot be reached because the interent connection is disrupted.
According to RFC 792, each TCP/IP host and router must respond to an ICMP Ping. If the destination is behind a firewall, however, there is a slight chance that ping packets are blocked, either because an overly anxious network administrator decided that hiding his host would be a good idea (security by obscurity), or because a Microsoft Windows Firewall is working at itīs default settings. In these cases it may be possible that the VoIP destination server is still working properly, even though he does not respond to ICMP Echo packets.
The colored status LEDs in GEOTEK phone book are showing the correct Asterisk registration status, by the way, no matter if the destination host is configured to answer ping requests or not.