Provided by: traceroute_2.1.0-2_amd64 bug


       traceroute - print the route packets trace to network host


       traceroute [-46dFITUnreAV] [-f first_ttl] [-g gate,...]
               [-i device] [-m max_ttl] [-p port] [-s src_addr]
               [-q nqueries] [-N squeries] [-t tos]
               [-l flow_label] [-w waittimes] [-z sendwait] [-UL] [-D]
               [-P proto] [--sport=port] [-M method] [-O mod_options]
               [--mtu] [--back]
               host [packet_len]
       traceroute6  [options]
       tcptraceroute  [options]
       lft  [options]


       traceroute tracks the route packets taken from an IP network on their way to a given host.
       It utilizes the IP protocol's time to live (TTL) field and  attempts  to  elicit  an  ICMP
       TIME_EXCEEDED response from each gateway along the path to the host.

       traceroute6 is equivalent to traceroute -6

       tcptraceroute is equivalent to traceroute -T

       lft  ,  the  Layer  Four  Traceroute,  performs a TCP traceroute, like traceroute -T , but
       attempts to provide compatibility with  the  original  such  implementation,  also  called

       The  only  required  parameter  is  the  name or IP address of the destination host .  The
       optional packet_len`gth is the total size of the probing packet (default 60 bytes for IPv4
       and  80 for IPv6). The specified size can be ignored in some situations or increased up to
       a minimal value.

       This program attempts to trace the route an IP packet would follow to some  internet  host
       by  launching  probe  packets  with  a small ttl (time to live) then listening for an ICMP
       "time exceeded" reply from a gateway.  We start our probes with a ttl of one and  increase
       by  one  until we get an ICMP "port unreachable" (or TCP reset), which means we got to the
       "host", or hit a max (which defaults to 30 hops). Three probes (by default)  are  sent  at
       each  ttl  setting and a line is printed showing the ttl, address of the gateway and round
       trip time of each probe. The address  can  be  followed  by  additional  information  when
       requested.  If  the  probe  answers  come  from  different  gateways,  the address of each
       responding system will be printed.  If there is no response within a certain  timeout,  an
       "*" (asterisk) is printed for that probe.

       After  the  trip  time,  some  additional  annotation can be printed: !H, !N, or !P (host,
       network or protocol unreachable), !S (source route failed), !F (fragmentation needed),  !X
       (communication   administratively   prohibited),   !V   (host  precedence  violation),  !C
       (precedence cutoff in effect), or !<num> (ICMP unreachable code <num>).  If almost all the
       probes result in some kind of unreachable, traceroute will give up and exit.

       We  don't  want  the destination host to process the UDP probe packets, so the destination
       port is set to an unlikely value (you can change it with the -p flag). There is no such  a
       problem  for  ICMP or TCP tracerouting (for TCP we use half-open technique, which prevents
       our probes to be seen by applications on the destination host).

       In the modern network environment the traditional traceroute methods  can  not  be  always
       applicable,  because of widespread use of firewalls.  Such firewalls filter the "unlikely"
       UDP ports, or even ICMP echoes.  To solve this, some additional tracerouting  methods  are
       implemented  (including tcp), see LIST OF AVAILABLE METHODS below. Such methods try to use
       particular protocol and source/destination port, in order to bypass firewalls (to be  seen
       by firewalls just as a start of allowed type of a network session).


       --help Print help info and exit.

       -4, -6 Explicitly  force  IPv4  or  IPv6 tracerouting. By default, the program will try to
              resolve the name given, and  choose  the  appropriate  protocol  automatically.  If
              resolving  a  host  name  returns both IPv4 and IPv6 addresses, traceroute will use

       -I, --icmp
              Use ICMP ECHO for probes

       -T, --tcp
              Use TCP SYN for probes

       -d, --debug
              Enable socket level debugging (when the Linux kernel supports it)

       -F, --dont-fragment
              Do not fragment probe  packets.  (For  IPv4  it  also  sets  DF  bit,  which  tells
              intermediate routers not to fragment remotely as well).

              Varying  the  size  of the probing packet by the packet_len command line parameter,
              you can manually obtain information about the MTU of individual network  hops.  The
              --mtu option (see below) tries to do this automatically.

              Note, that non-fragmented features (like -F or --mtu) work properly since the Linux
              kernel 2.6.22 only.  Before that version, IPv6 was always  fragmented,  IPv4  could
              use  the  once  the  discovered final mtu only (from the route cache), which can be
              less than the actual mtu of a device.

       -f first_ttl, --first=first_ttl
              Specifies with what TTL to start. Defaults to 1.

       -g gateway, --gateway=gateway
              Tells traceroute to add an IP source routing option to  the  outgoing  packet  that
              tells  the  network to route the packet through the specified gateway (most routers
              have disabled source routing for security reasons).  In general, several  gateway's
              is  allowed  (comma separated). For IPv6, the form of num,addr,addr...  is allowed,
              where num is a route header type (default is type 2). Note the type 0 route  header
              is now deprecated (rfc5095).

       -i interface, --interface=interface
              Specifies  the  interface through which traceroute should send packets. By default,
              the interface is selected according to the routing table.

       -m max_ttl, --max-hops=max_ttl
              Specifies the maximum number of  hops  (max  time-to-live  value)  traceroute  will
              probe. The default is 30.

       -N squeries, --sim-queries=squeries
              Specifies  the  number  of  probe packets sent out simultaneously.  Sending several
              probes concurrently can speed up traceroute considerably. The default value is 16.
              Note that some routers and hosts can use ICMP rate throttling. In such a  situation
              specifying too large number can lead to loss of some responses.

       -n     Do not try to map IP addresses to host names when displaying them.

       -p port, --port=port
              For  UDP  tracing,  specifies  the  destination  port base traceroute will use (the
              destination port number will be incremented by each probe).
              For ICMP tracing, specifies the initial ICMP sequence value  (incremented  by  each
              probe too).
              For  TCP and others specifies just the (constant) destination port to connect. When
              using the tcptraceroute wrapper, -p specifies the source port.

       -t tos, --tos=tos
              For IPv4, set the Type of Service (TOS) and Precedence value. Useful values are  16
              (low  delay) and 8 (high throughput). Note that in order to use some TOS precedence
              values, you have to be super user.
              For IPv6, set the Traffic Control value.

       -l flow_label, --flowlabel=flow_label
              Use specified flow_label for IPv6 packets.

       -w max[,here,near], --wait=max[,here,near]
              Determines how long to wait for a response to a probe.

              There are three (in general) float values separated by a comma (or a  slash).   Max
              specifies the maximum time (in seconds, default 5.0) to wait, in any case.

              Traditional  traceroute  implementation  always  waited  whole  max seconds for any
              probe. But if we already have some replies from the same hop,  or  even  from  some
              next hop, we can use the round trip time of such a reply as a hint to determine the
              actual reasonable amount of time to wait.

              The optional here (default 3.0) specifies a factor to multiply the round trip  time
              of an already received response from the same hop. The resulting value is used as a
              timeout for the probe, instead of (but  no  more  than)  max.   The  optional  near
              (default  10.0) specifies a similar factor for a response from some next hop.  (The
              time of the first found result is used in both cases).

              First, we look for the same hop (of the probe which  will  be  printed  first  from
              now).   If  nothing  found, then look for some next hop. If nothing found, use max.
              If here and/or near have zero values, the corresponding computation is skipped.
              Here and near are always set to zero if only max is  specified  (for  compatibility
              with previous versions).

       -q nqueries, --queries=nqueries
              Sets the number of probe packets per hop. The default is 3.

       -r     Bypass  the  normal  routing  tables  and  send  directly  to a host on an attached
              network.  If the host is not on a directly-attached network, an error is  returned.
              This option can be used to ping a local host through an interface that has no route
              through it.

       -s source_addr, --source=source_addr
              Chooses an alternative source address. Note that you must select the address of one
              of the interfaces.  By default, the address of the outgoing interface is used.

       -z sendwait, --sendwait=sendwait
              Minimal  time  interval  between probes (default 0).  If the value is more than 10,
              then it specifies a number in milliseconds, else it is a number of  seconds  (float
              point  values  allowed  too).   Useful  when  some  routers use rate-limit for ICMP

       -e, --extensions
              Show ICMP extensions (rfc4884). The general  form  is  CLASS/TYPE:  followed  by  a
              hexadecimal   dump.    The   MPLS   (rfc4950)   is   shown   parsed,   in  a  form:
              MPLS:L=label,E=exp_use,S=stack_bottom,T=TTL (more objects separated by / ).

       -A, --as-path-lookups
              Perform AS path lookups in routing registries and print results directly after  the
              corresponding addresses.

       -V, --version
              Print the version and exit.

       There  are additional options intended for advanced usage (such as alternate trace methods

              Chooses the source port to use. Implies -N 1 -w 5  .   Normally  source  ports  (if
              applicable) are chosen by the system.

              Set the firewall mark for outgoing packets (since the Linux kernel 2.6.25).

       -M method, --module=name
              Use  specified method for traceroute operations. Default traditional udp method has
              name default, icmp (-I) and tcp (-T) have names icmp and tcp respectively.
              Method-specific options can be passed by  -O .   Most  methods  have  their  simple
              shortcuts, (-I means -M icmp, etc).

       -O option, --options=options
              Specifies  some  method-specific option. Several options are separated by comma (or
              use several -O on cmdline).  Each method may have its own specific options, or many
              not have them at all.  To print information about available options, use -O help.

       -U, --udp
              Use  UDP to particular destination port for tracerouting (instead of increasing the
              port per each probe). Default port is 53 (dns).

       -UL    Use UDPLITE for tracerouting (default port is 53).

       -D, --dccp
              Use DCCP Requests for probes.

       -P protocol, --protocol=protocol
              Use raw packet of specified protocol for  tracerouting.  Default  protocol  is  253

       --mtu  Discover MTU along the path being traced. Implies -F -N 1.  New mtu is printed once
              in a form of F=NUM at the first probe of a  hop  which  requires  such  mtu  to  be
              reached.  (Actually,  the correspond "frag needed" icmp message normally is sent by
              the previous hop).

              Note, that some routers might cache once the seen information on  a  fragmentation.
              Thus  you  can  receive the final mtu from a closer hop.  Try to specify an unusual
              tos by -t , this can help for one attempt (then it can be cached there as well).
              See -F option for more info.

       --back Print the number of  backward  hops  when  it  seems  different  with  the  forward
              direction. This number is guessed in assumption that remote hops send reply packets
              with initial ttl set to either 64, or 128 or 255 (which seems a  common  practice).
              It is printed as a negate value in a form of '-NUM' .


       In  general,  a particular traceroute method may have to be chosen by -M name, but most of
       the methods have their simple cmdline switches (you can see them after the method name, if

       The traditional, ancient method of tracerouting. Used by default.

       Probe  packets  are  udp  datagrams  with  so-called  "unlikely"  destination  ports.  The
       "unlikely" port of the first probe is 33434, then for each next probe it is incremented by
       one.  Since  the  ports  are  expected to be unused, the destination host normally returns
       "icmp unreach port" as a final response.  (Nobody knows what happens when some application
       listens for such ports, though).

       This method is allowed for unprivileged users.

   icmp       -I
       Most usual method for now, which uses icmp echo packets for probes.
       If you can ping(8) the destination host, icmp tracerouting is applicable as well.

       This  method  may  be  allowed for unprivileged users since the kernel 3.0 (IPv4, for IPv6
       since 3.11), which supports new dgram icmp (or "ping") sockets.  To  allow  such  sockets,
       sysadmin  should  provide net/ipv4/ping_group_range sysctl range to match any group of the

       raw    Use only raw sockets (the traditional way).
              This way is tried first by default (for compatibility reasons), then new dgram icmp
              sockets as fallback.

       dgram  Use only dgram icmp sockets.

   tcp        -T
       Well-known modern method, intended to bypass firewalls.
       Uses the constant destination port (default is 80, http).

       If  some  filters  are  present in the network path, then most probably any "unlikely" udp
       ports (as for default method) or even icmp echoes (as for icmp) are  filtered,  and  whole
       tracerouting  will  just  stop at such a firewall.  To bypass a network filter, we have to
       use only allowed protocol/port combinations. If we trace for some, say,  mailserver,  then
       more likely -T -p 25 can reach it, even when -I can not.

       This  method  uses  well-known  "half-open  technique", which prevents applications on the
       destination host from seeing our probes at all.  Normally, a tcp syn  is  sent.  For  non-
       listened  ports  we  receive  tcp  reset,  and  all is done. For active listening ports we
       receive tcp syn+ack, but answer by tcp reset (instead of expected tcp ack), this  way  the
       remote tcp session is dropped even without the application ever taking notice.

       There is a couple of options for tcp method:

              Sets specified tcp flags for probe packet, in any combination.

              Sets the flags field in the tcp header exactly to num.

       ecn    Send  syn  packet with tcp flags ECE and CWR (for Explicit Congestion Notification,

              Use the corresponding tcp header option in the outgoing probe packet.

       sysctl Use current sysctl (/proc/sys/net/*) setting for the tcp header options  above  and
              ecn.  Always set by default, if nothing else specified.

              Use value of num for maxseg tcp header option (when syn).

       info   Print  tcp  flags  of final tcp replies when the target host is reached.  Allows to
              determine whether an application listens the port and other useful things.

       Default options is syn,sysctl.

       An initial implementation of tcp method, simple using connect(2) call, which does full tcp
       session  opening.  Not  recommended  for  normal use, because a destination application is
       always affected (and can be confused).

   udp        -U
       Use udp datagram with constant destination port (default 53, dns).
       Intended to bypass firewall as well.

       Note, that unlike in tcp method, the correspond application on the destination host always
       receive our probes (with random data), and most can easily be confused by them. Most cases
       it will not respond to our packets though, so we will never  see  the  final  hop  in  the
       trace. (Fortunately, it seems that at least dns servers replies with something angry).

       This method is allowed for unprivileged users.

   udplite    -UL
       Use udplite datagram for probes (with constant destination port, default 53).

       This method is allowed for unprivileged users.

              Set udplite send coverage to num.

   dccp    -D
       Use DCCP Request packets for probes (rfc4340).

       This  method uses the same "half-open technique" as used for TCP.  The default destination
       port is 33434.


              Set DCCP service code to num (default is 1885957735).

   raw        -P proto
       Send raw packet of protocol proto.
       No protocol-specific headers are used, just IP header only.
       Implies -N 1 -w 5 .

              Use IP protocol proto (default 253).


       To speed up work, normally several probes are sent simultaneously.  On the other hand,  it
       creates a "storm of packages", especially in the reply direction. Routers can throttle the
       rate of icmp responses, and some of replies can be  lost.  To  avoid  this,  decrease  the
       number  of  simultaneous  probes,  or  even  set  it  to  1  (like  in  initial traceroute
       implementation), i.e.  -N 1

       The final (target) host can drop some of the simultaneous probes, and  might  even  answer
       only  the  latest ones. It can lead to extra "looks like expired" hops near the final hop.
       We use a smart algorithm to auto-detect such a situation, but if it cannot  help  in  your
       case, just use -N 1 too.

       For  even greater stability you can slow down the program's work by -z option, for example
       use -z 0.5 for half-second pause between probes.

       To avoid an extra waiting, we use adaptive algorithm for timeouts (see -w option for  more
       info).  It  can  lead to premature expiry (especially when response times differ at times)
       and printing "*" instead of a time.  In  such  a  case,  switch  this  algorithm  off,  by
       specifying -w with the desired timeout only (for example, -w 5).

       If  some  hops  report nothing for every method, the last chance to obtain something is to
       use ping -R command (IPv4, and for nearest 8 hops only).


       ping(8), ping6(8), tcpdump(8), netstat(8)