inetutils.info: traceroute invocation

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8 'traceroute': Trace the route to a host
*****************************************

'traceroute' prints a trace of the route IP packets are travelling to a
remote host.

Synopsis:

     traceroute [OPTION...] HOST

8.1 Command line options
========================

'-f NUM'
'--first-hop=NUM'
     Set the initial hop distance to NUM, instead of the default 1.
     This immediately allows probing packets to sense routing properties
     closer to the target host, skipping routers close to the local
     host.  Quicker analysis of problems known to lie at some routing
     distance is the outcome.

'-g GATES'
'--gateways=GATES'
     Set intermediary hosts used in loose source routing.  The argument
     GATES is a list of gateways, using spaces, commata, or semicola as
     separators.  These hosts must be traversed in the given order
     before the intended host receives any datagram.  At most eight host
     names or addresses may be specified.  Multiple uses of '-g' produce
     a concatenated list.

'-I'
'--icmp'
     Use ICMP ECHO datagrams for probing the remote host.

'-m NUM'
'--max-hop=NUM'
     Set the maximum time-to-live allowed for probing.  In other words,
     stop probing when the hop distance is in excess of NUM.  The
     default limit is 64.

'-M METHOD'
'--type=METHOD'
     Use METHOD as carrier packets for traceroute operations.  Supported
     choices are 'icmp' and 'udp', where 'udp' is the default type.

'-p PORT'
'--port=PORT'
     Set destination port of target to PORT.  The default value is
     33434.

'-q NUM'
'--tries=NUM'
     Send a total of NUM probe packets per hop, defaulting to 3.

'--resolve-hostnames'
     Attempt to resolve all addresses as hostnames.

'-t NUM'
'--tos=NUM'
     Set type-of-service, TOS field, to NUM on transmitted packets.

'-w NUM'
'--wait=NUM'
     Set timeout in seconds, within which a returning response packet is
     accepted as such.  Default waiting time is three seconds.

8.2 Diagnostic tokens
=====================

During execution, 'traceroute' sends three datagrams for each value for
the TTL field, printing a diagnostic line of output for these.  The TTL
field is then steadily increased until the intended host responds, or
some intermediary gateway returns a datagram to the effect that the
target cannot be reached due to one reason or another.

   Each line of output displays a sequence number, followed by
diagnostic annotation.  Any responding host has its address printed
without repetition, together with a measured timing.  In case there is
no response within a time period of three seconds, an asterisque '*' is
printed.

   When an intermediate router responds with an exceptional state, the
time elapsed since emitting the original datagram is printed, followed
by an additional short hand hint of the reason:

'!F'
     Fragmentation needed by gateway.

'!H'
     Host not reachable from gateway.

'!N'
     Network not reachable from gateway.

'!P'
     Protocol not usable at host, or within network.

'!S'
     Source routing failed at gateway.

'!T'
     Host or network not reachable for stated type of service, TOS.

'!U'
     Isolated host, not reachable.

'!X'
     Forbidden by remote administration.