TRACEROUTE(1)                     Traceroute For Linux                    TRACEROUTE(1)

NAME
       traceroute - print the route packets trace to network host

SYNOPSIS
       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]

DESCRIPTION
       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 "lft".

       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 situ‐
       ations or increased up to a minimal value.

       This  program  attempts to trace the route an IP packet would follow to some in‐
       ternet host by launching probe packets with a small ttl (time to live) then lis‐
       tening  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  (fragmen‐
       tation  needed), !X (communication administratively prohibited), !V (host prece‐
       dence 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 des‐
       tination  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 des‐
       tination host).

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

OPTIONS
       --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 auto‐
              matically. If resolving a host name returns both IPv4 and IPv6 addresses,
              traceroute will use IPv4.

       -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 pa‐
              rameter,  you can manually obtain information about the MTU of individual
              network hops. The --mtu option (see below) tries  to  do  this  automati‐
              cally.

              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 frag‐
              mented,  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 de‐
              fault 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 con‐
              nect. 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 val‐
              ues 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  result‐
              ing  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 com‐
              patibility 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  at‐
              tached  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 ad‐
              dress 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 messages.

       -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 etc.):

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

       --fwmark=mark
              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 spe‐
              cific 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 in‐
              creasing 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 (rfc3692).

       --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  re‐
              quires  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  frag‐
              mentation.  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 for‐
              ward 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' .

LIST OF AVAILABLE METHODS
       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 present).

   default
       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 al‐
       low such sockets, sysadmin should provide net/ipv4/ping_group_range sysctl range
       to match any group of the user.
       Options:

       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  "un‐
       likely"  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  ex‐
       pected tcp ack), this way the remote tcp session is dropped even without the ap‐
       plication ever taking notice.

       There is a couple of options for tcp method:

       syn,ack,fin,rst,psh,urg,ece,cwr
              Sets specified tcp flags for probe packet, in any combination.

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

       ecn    Send syn packet with tcp flags ECE and CWR (for Explicit Congestion Noti‐
              fication, rfc3168).

       sack,timestamps,window_scaling
              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.

       mss=num
              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.

   tcpconn
       An initial implementation of tcp method, simple  using  connect(2)  call,  which
       does  full tcp session opening. Not recommended for normal use, because a desti‐
       nation 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 con‐
       fused 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.
       Options:

       coverage=num
              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.

       Options:

       service=num
              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 .
       Options:

       protocol=proto
              Use IP protocol proto (default 253).

NOTES
       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 some‐
       thing is to use ping -R command (IPv4, and for nearest 8 hops only).

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

Traceroute                          11 October 2006                       TRACEROUTE(1)

Usage:
  traceroute [ -46dFITnreAUDV ] [ -f first_ttl ] [ -g gate,... ] [ -i device ] [ -m max_ttl ] [ -N squeries ] [ -p port ] [ -t tos ] [ -l flow_label ] [ -w MAX,HERE,NEAR ] [ -q nqueries ] [ -s src_addr ] [ -z sendwait ] [ --fwmark=num ] host [ packetlen ]
Options:
  -4                          Use IPv4
  -6                          Use IPv6
  -d  --debug                 Enable socket level debugging
  -F  --dont-fragment         Do not fragment packets
  -f first_ttl  --first=first_ttl
                              Start from the first_ttl hop (instead from 1)
  -g gate,...  --gateway=gate,...
                              Route packets through the specified gateway
                              (maximum 8 for IPv4 and 127 for IPv6)
  -I  --icmp                  Use ICMP ECHO for tracerouting
  -T  --tcp                   Use TCP SYN for tracerouting (default port is 80)
  -i device  --interface=device
                              Specify a network interface to operate with
  -m max_ttl  --max-hops=max_ttl
                              Set the max number of hops (max TTL to be
                              reached). Default is 30
  -N squeries  --sim-queries=squeries
                              Set the number of probes to be tried
                              simultaneously (default is 16)
  -n                          Do not resolve IP addresses to their domain names
  -p port  --port=port        Set the destination port to use. It is either
                              initial udp port value for "default" method
                              (incremented by each probe, default is 33434), or
                              initial seq for "icmp" (incremented as well,
                              default from 1), or some constant destination
                              port for other methods (with default of 80 for
                              "tcp", 53 for "udp", etc.)
  -t tos  --tos=tos           Set the TOS (IPv4 type of service) or TC (IPv6
                              traffic class) value for outgoing packets
  -l flow_label  --flowlabel=flow_label
                              Use specified flow_label for IPv6 packets
  -w MAX,HERE,NEAR  --wait=MAX,HERE,NEAR
                              Wait for a probe no more than HERE (default 3)
                              times longer than a response from the same hop,
                              or no more than NEAR (default 10) times than some
                              next hop, or MAX (default 5.0) seconds (float
                              point values allowed too)
  -q nqueries  --queries=nqueries
                              Set the number of probes per each hop. Default is
                              3
  -r                          Bypass the normal routing and send directly to a
                              host on an attached network
  -s src_addr  --source=src_addr
                              Use source src_addr for outgoing packets
  -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)
  -e  --extensions            Show ICMP extensions (if present), including MPLS
  -A  --as-path-lookups       Perform AS path lookups in routing registries and
                              print results directly after the corresponding
                              addresses
  -M name  --module=name      Use specified module (either builtin or external)
                              for traceroute operations. Most methods have
                              their shortcuts (`-I' means `-M icmp' etc.)
  -O OPTS,...  --options=OPTS,...
                              Use module-specific option OPTS for the
                              traceroute module. Several OPTS allowed,
                              separated by comma. If OPTS is "help", print info
                              about available options
  --sport=num                 Use source port num for outgoing packets. Implies
                              `-N 1'
  --fwmark=num                Set firewall mark for outgoing packets
  -U  --udp                   Use UDP to particular port for tracerouting
                              (instead of increasing the port per each probe),
                              default port is 53
  -UL                         Use UDPLITE for tracerouting (default dest port
                              is 53)
  -D  --dccp                  Use DCCP Request for tracerouting (default port
                              is 33434)
  -P prot  --protocol=prot    Use raw packet of protocol prot for tracerouting
  --mtu                       Discover MTU along the path being traced. Implies
                              `-F -N 1'
  --back                      Guess the number of hops in the backward path and
                              print if it differs
  -V  --version               Print version info and exit
  --help                      Read this help and exit

Arguments:
+     host          The host to traceroute to
      packetlen     The full packet length (default is the length of an IP
                    header plus 40). Can be ignored or increased to a minimal
                    allowed value