Sometimes, there is a problem with routing propogation,
and some sites are unable to connect to you. Perhaps the
most useful command for trying to figure out where a
routing is breaking down is the traceroute(8)
command. It is equally useful if you cannot seem to make
a connection to a remote machine (ie. ping(8)
fails).
The traceroute(8) command is run with the name
of the remote host you are trying to connect to. It will
show the gateway hosts along the path of the attempt,
eventually either reaching the target host, or
terminating because of a lack of connection.
For more information, see the manual page for
traceroute(8).