traceroute

Description

Use the traceroute command to trace the route that packets take to a destination.

Syntax

traceroute [<traceroute options>] <host> [<packet-length>]

Arguments

 

<traceroute options>	Enter one of the following options: • -4: Use IPv4. • -6: Use IPv6. • -A: Perform AS path lookups in routing registries and print results directly after the corresponding addresses. • -f: Set the initial time-to-live used in the first outgoing probe packet. • -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. • -d: Enable socket level debugging. • -g: Specify a loose source route gateway (8 maximum). • -i: Specify a network interface to obtain the source IP address for outgoing probe packets. This is normally only useful on a multi-homed host. (See the -s flag for another way to do this.) • -I: Use ICMP ECHO instead of UDP datagrams. • -l: Use specified flow_label for IPv6 packets. • -m: Set the max time-to-live (max number of hops) used in outgoing probe packets. The default is 30 hops (the same default used for TCP connections). • -n: Print hop addresses numerically rather than symbolically and numerically (saves a nameserver address-to-name lookup for each gateway found on the path). • -N: The number of probe packets sent out simultaneously. Sending several probes concurrently can speed up traceroute considerably. Default = 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. • -p: Set the base UDP port number used in probes (default is 33434). Traceroute hopes that nothing is listening on UDP ports base to base + nhops - 1 at the destination host (so an ICMP PORT_UNREACHABLE message will be returned to terminate the route tracing). If something is listening on a port in the default range, this option can be used to pick an unused port range. • -q: nqueries
	• -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 (for example, after the interface was dropped by routed(8C)). • -s: Use the following IP address (which usually is given as an IP number, not a hostname) as the source address in outgoing probe packets. On multi-homed hosts (those with more than one IP address), this option can be used to force the source address to be something other than the IP address of the interface the probe packet is sent on. If the IP address is not one of this machine’s interface addresses, an error is returned and nothing is sent. (See the -i flag for another way to do this.) • -t: Set the type-of-service in probe packets to the following value (default zero). The value must be a decimal integer in the range 0 to 255. This option can be used to see if different types-of-service result in different paths. (If you are not running 4.4bsd, this may be academic since the normal network services like telnet and ftp don’t let you control the TOS). Not all values of TOS are legal or meaningful - see the IP spec for definitions. If TOS value is changed by intermediate routers, (TOS=<value>!) will be printed once: value is the decimal value of the changed TOS byte. • -T: Use TCP SYN for tracerouting. • -U: Use UDP datagram (default) for tracerouting. • -V: Print version info and exit. • -w: Set the time (in seconds) to wait for a response to a probe (default 5 sec.). • -z: Set the time (in milliseconds) to pause between probes (default 0). Some systems such as Solaris and routers such as Ciscos rate limit icmp messages. A good value to use with this is 500 (e.g. 1/2 second).
<host>	Specifies the name, alias, or Internet address of the remote host.
<packet-length>	Specifies the packet length in bytes.

Defaults

The default packet length is 40 bytes.

Command Mode

User EXEC Mode

Privileged EXEC Mode

Global Configuration Mode

See Also

See the following related commands:

n

“hping2”

n

“mtr”

n

“ping”

n

“tcpdump”

n	“tcptraceroute”

n	“traceroute”

Usage Guidelines

None.

Examples

None.

 

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