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Name

traceroute - print the route packets take to network host

Synopsis

traceroute [-46FnrRV] [-f first_ttl] [-p port] [-m max_hops] [-N concurrent_hops] [-t tos] [-w timeout] [-q nqueries] [-s source_addr] [-i interface]
[-g gateway] host [packetlen]
traceroute6 [options]

Description

traceroute tracks the route packets take across a TCP/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 just another name for the same program, and is equivalent to invoking traceroute with the -6 option.

Options

The only required parameter is the name or IP address of the destination 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.

Additional options are:

-6, -4 Explicitly
force IPv4 or IPv6 traceouting. 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 IPv4. Invoking the program as traceroute6 is the same as using the -6 option.

-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 outgoing 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 to traceroute should send packets. By default, the interface is selected according to the routing table.

-m max_hops
Specifies the maximum number of hops traceroute will probe. The default value is 30.

-N concurrent_hops
Specifies the number of probe packets sent out simultaneously. Sending several probes concurrently can speed up traceroute considerably. However, when specifying a number that’s too large, the destination host will start to throw away random ICMP responses (if it implements ICMP rate throttling), and tracer_oute will be unable to detect the final hope reliably. The default value is 6.

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

-p port
Specifies the UDP destination port base traceroute will use. When sending its UDP probe packets, it will send them to port + hop - 1 for each hop. If there are ports in this range in use on the destination host, traceroute will not be able to identify reliably when it has reached the destination host (probes will appear to time out). The default port is 33434; you can use -p to change this to a different value.

-t tos Set the IP 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.

-w sec Wait for sec seconds before sending the next probe packet.

Note that unlike older traceroute versions, this implementation will transmit several probe packets in parallel, for different hop values. However, it will never send more than 1 packet per hop value at the same time.

-q numqueries
Sets the number of probe packets per hop. The default value 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.

-R
Set the loose source route option on outgoing packets, asking intermediate routers to record their address as the packet passes. This can be useful if you want to find the address of an intermediate router that has been configured to not respond to traceroute packets.

This feature hasn’t been implemented yet.

-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.

-V
Print the version and exit.

See Also

ping(8) , netstat(8) .

Author

Concept and command line options based on the original LBL implementation of traceroute, written by Van Jacobson. This implentation is a complete rewrite and redesign, written and copyright (C) 2000 Olaf Kirch <okir@suse.de>.


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