(ttl=n!)

    This indicates that the ttl value in the ICMP "time exceeded"
    packet that we received was unexpected. We expected some initial
    value, for example, the number of routers between our system and
    another system. In other words, if the path from hop 5 to us is
    the same as the path from us to hop 5, we expect to receive a ttl
    value of 4.

    There are several common initial values for ICMP ttls: 255, 60,
    59, 30 and 29. 4.3 tahoe BSD and Cisco routers use 255, Proteon
    routers use either 59 or 29 depending on software release,
    several other implementations use 60 and 30. Tru64 UNIX uses an
    initial ttl of 64. The traceroute command checks against all of
    these, making it hard to detect some small routing asymmetries.
    If you want to see the ttl values in all the packets, use the -l
    option.

                                   NOTE

       This program is intended for use in network testing,
       measurement and management. It should be used primarily
       for manual fault isolation. Because of the load it could
       impose on the network, do not use traceroute during normal
       operations or from automated scripts.