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TRACEROUTE(8)		       Fedora Core Linux		 TRACEROUTE(8)



NAME
       traceroute - print the route packets trace to network host

SYNOPSIS
       traceroute [-46dFITUnrAV] [-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 waittime] [-z sendwait]
	       host [packetlen]
       traceroute6  [options]
       tracert	[options]
       tcptraceroute  [options]

DESCRIPTION
       traceroute  tracks the route packets take across 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 equivalents to traceroute -6
       tracert equivalents to traceroute -I
       tcptraceroute equivalents to traceroute -T -p 80

OPTIONS
       The only required parameter is the name or IP address of	 the  destina-
       tion  host.  This  paremeter can be followed by the size of the probing
       packet sent to that host (40 by	default).  Varying  the	 size  of  the
       packet  in  conjunction	with  the  -F  parameter can be used to obtain
       information about the MTU of individual network hops. (The size parame-
       ter is useless for TCP probes).

       Additional options are:

       --help Print help info and exit.

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

       -I     Use ICMP ECHO for probes

       -T     Use TCP SYN for probes

       -U     Use UDP datagrams for probes (it is default). Only UDP method is
	      allowed for unprivileged users.

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

       -F     Set the "Don't Fragment" bit. This  tells	 intermediate  routers
	      not  to  fragment	 the  packet when they find it's too big for a
	      network hop's MTU.

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

       -g gateway
	      Tells traceroute to add an IP source routing option to the  out-
	      going  packet that tells the network to route the packet through
	      the specified gateway.  Not very useful,	because	 most  routers
	      have disabled source routing for security reasons.

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

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

       -N squeries
	      Specifies the number of probe packets sent  out  simultaneously.
	      Sending several probes concurrently can speed up traceroute con-
	      siderably. The default value is 15.
	      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
	      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 specifies just the (constant) destination port  to  con-
	      nect.

       -t 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 precendence values, you have to be
	      super user.
	      For IPv6, set the Traffic Control value.

       -w waittime
	      Set the time (in seconds) to wait for  a	response  to  a	 probe
	      (default 5.0 sec).

       -q 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
	      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
	      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.

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

       -V     Print the version and exit.

       This  program  attempts to trace the route an IP packet would follow to
       some internet host by launching a probe packets with a small ttl	 (time
       to  live) then listening for an ICMP "time exceeded" reply from a gate-
       way.  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
       "host", or hit a max (which defaults to 30 hops).  Three	 (by  default)
       probes  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.  If  the
       probe  answers  come  from  different  gateways,	 the  address  of each
       responding system will be printed.  If there is no  response  within  a
       5.0 (default) seconds, a "*" is printed for that probe.

       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 problem for ICMP or TCP tracerout-
       ing (for TCP we close sessions immediately after connect).

       After the 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.

SEE ALSO
       ping(8), ping6(8), tracepath(8), netstat(8).



Fedora Project			11 October 2006			 TRACEROUTE(8)
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