TRACEROUTE(8) Maintenance Procedures TRACEROUTE(8)


traceroute - print the route packets take to network host


traceroute [-adFIlnSvx] [-A addr_family] [-c traffic_class]
[-f first_hop] [-g gateway [-g gateway...] | -r]
[-i iface] [-L flow_label] [-m max_hop]
[-P pause_sec] [-p port] [-Q max_timeout]
[-q nqueries] [-s src_addr] [-t tos] [-w wait_time] host


The Internet is a large and complex aggregation of network hardware,
connected by gateways. Tracking the route a packet follows can be
difficult. The utility traceroute traces the route that an IP packet
follows to another internet host.

The traceroute utility utilizes the both the IPv4 and IPv6 protocols. Use
the -A option to override the default behavior. traceroute uses the IPv4
protocol ttl (time to live) field or the IPv6 field hop limit. It
attempts to elicit an ICMP or ICMP6 TIME_EXCEEDED response from each
gateway along the path, and a PORT_UNREACHABLE(or ECHO_REPLY if -I is
used) response from the destination host. It starts by sending probes
with a ttl or hop limit of 1 and increases by 1 until it either gets to
the host, or it hits the maximum max_hop. The default maximum max_hop is
30 hops, but this can be set by the -m option.

Three probes are sent at each ttl (hop limit) setting, and a line is
printed showing the ttl (hop limit), the hostname and the address of the
gateway, and the rtt (round trip time) of each probe. The number of
probes may be specifically set using the -q option. If the probe answers
come from different gateways, the hostname and the address of each
responding system will be printed. If there is no response within a 5
second timeout interval, an asterisk (*) is displayed for that probe. The
-w option may be used to set the timeout interval. Other possible
annotations that may appear after the time are:


the ttl (hop limit) value in the received packet is <= 1.


host unreachable.


communication administratively prohibited.


ICMP (ICMP6) unreachable code N.

The following annotations appear only for IPv4:


fragmentation needed. This should never occur. If this is seen, the
associated gateway is broken.


network unreachable.


protocol unreachable.


source route failed. It is likely that the gateway does not support
source routing.


unreachable for the specified tos (type-of-service).


source host isolated or precedence problem.

The following annotations appear only for IPv6:


host unreachable for a reason other than lack of an entry in the
routing table.


packet too big.


destination is not a neighbor.


unrecognized next header.

If almost all the probes result in some kind of unreachable code, then
traceroute gives up and exits.

The destination host is not supposed to process the UDP probe packets, so
the destination port default is set to an unlikely value. However, if
some application on the destination is using that value, the value of
port can be changed with the -p option.

The only mandatory parameter is the destination host name or IP number.
The default probe datagram length is 40 bytes (60 bytes for IPv6), but
this may be increased by specifying a packet length (in bytes) after the
destination host name.

All integer arguments to traceroute can be specified in either decimal or
hexadecimal notation. For example, packetlen can be specified either as
256 or 0x100.


-A addr_family

Specify the address family of the target host. addr_family can be
either inet or inet6. Address family determines which protocol to
use. For an argument of inet, IPv4 is used. For inet6, IPv6 is used.

By default, if the name of a host is provided, not the literal IP
address, and a valid IPv6 address exists in the name service
database, traceroute will use this address. Otherwise, if the name
service database contains an IPv4 address, it will try the IPv4

Specify the address family inet or inet6 to override the default
behavior. If the argument specified is inet, traceroute will use the
IPv4 address associated with the hostname. If none exists, traceroute
will state that the host is unknown and exit. It will not try to
determine if an IPv6 address exists in the name service database.

If the specified argument is inet6, traceroute will use the IPv6
address that is associated with the hostname. If none exists,
traceroute will state that the host is unknown and exit.


Probe all of the addresses of a multi-homed destination. The output
looks like traceroute has been run once for each IP address of the
destination. If this option is used together with -A, traceroute
probes only the addresses that are of the specified address family.
While probing one of the addresses of the destination, user can skip
to the next address by sending a SIGINT, or exit traceroute by
sending a SIGQUIT signal. See signal(3C)

-c traffic_class

Specify the traffic class of probe packets. The value must be an
integer in the range from 0 to 255. Gateways along the path may route
the probe packet differently depending upon the value of
traffic_class set in the probe packet. This option is valid only on


Set the SO_DEBUG socket option.


Set the "don't fragment" bit. This option is valid only on IPv4. When
specified from within a shared-IP zone, this option has no effect as
the "don't fragment" bit is always set in this case.

-f first_hop

Set the starting ttl (hop limit) value to first_hop, to override the
default value 1. traceroute skips processing for those intermediate
gateways which are less than first_hop hops away.

-g gateway

Specify a loose source route gateway. The user can specify more than
one gateway by using -g for each gateway. The maximum number of
gateways is 8 for IPv4 and 127 for IPv6. Note that some factors such
as the link MTU can further limit the number of gateways for IPv6.
This option cannot be used with the -r option.

Only users with the {PRIV_NET_RAWACCESS} privilege can specify a
loose source route with this option.


Use ICMP (ICMP6) ECHO instead of UDP datagrams.

-i iface

For IPv4, this option specifies a network interface to obtain the
source IP address. This is normally only useful on a multi-homed
host. The -s option is also another way to do this. For IPv6, it
specifies the network interface on which probe packets are
transmitted. The argument can be either an interface index, for
example, 1, 2, or an interface name, for example, eri0, hme0.

-L flow_label

Specify the flow label of probe packets. The value must be an integer
in the range from 0 to 1048575. This option is valid only on IPv6.


Print the value of the ttl (hop limit) field in each packet received.

-m max_hop

Set the maximum ttl (hop limit) used in outgoing probe packets. The
default is 30 hops, which is the same default used for TCP


Print hop addresses numerically rather than symbolically and
numerically. This saves a nameserver address-to-name lookup for each
gateway found on the path.

-P pause_sec

Specify a delay, in seconds, to pause between probe packets. This may
be necessary if the final destination does not accept undeliverable
packets in bursts. By default, traceroute sends the next probe as
soon as it has received a reply. Note that pause_sec is a real

-p port

Set the base UDP port number used in probes.The default is 33434.
traceroute hopes that nothing is listening on UDP ports
(base+(nhops-1)*nqueries) to (base+(nhops*nqueries)-1) at the
destination host, so that an ICMP (ICMP6) 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
select an unused port range. nhops is defined as the number of hops
between the source and the destination.

-Q max_timeout

Stop probing this hop after max_timeout consecutive timeouts are
detected. The default value is 5. Useful in combination with the -q
option if you have specified a large nqueries probe count.

-q nqueries

Set the desired number of probe queries. The default is 3.


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 send probes to a
local host through an interface that has been dropped by the router
daemon. See in.routed(8). You cannot use this option if the -g
option is used.


Display a summary of how many probes were not answered for each hop.

-s src_addr

Use the following address, which usually is given as a literal IP
address, 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 traceroute picks by default. If the IP
address is not one of this machine's interface addresses, an error is
returned and nothing is sent. For IPv4, when used together with the
-i option, the given IP address should be configured on the specified
interface. Otherwise, an error will be returned. In the case of IPv6,
the interface name and the source address do not have to match.

-t tos

Set the tos(type-of-service) in probe packets to the specified value.
The default is zero. The value must be an integer in the range from 0
to 255. Gateways along the path may route the probe packet
differently depending upon the tos value set in the probe packet.
This option is valid only on IPv4.


Verbose output. For each hop, the size and the destination of the
response packets is displayed. Also ICMP (ICMP6) packets received
other than TIME_EXCEEDED and UNREACHABLE are listed as well.

-w waittime

Set the time, in seconds, to wait for a response to a probe. The
default is 5 seconds.


Prevent traceroute from calculating checksums. Checksums are usually
required for the last hop when using ICMP ECHO probes. This option is
valid only on IPv4. See the -I option.

When specified from within a shared-IP zone, this option has no
effect as the checksum is always calculated by the operating system
in this case.


The following operands are supported:


The network host.


Example 1: Sample Output From the traceroute Utility

Some sample output from the traceroute utility might be:

istanbul% traceroute london
traceroute: Warning: london has multiple addresses; \
using 4::114:a00:20ff:ab3d:83ed
traceroute: Warning: Multiple interfaces found; \
using 4::56:a00:20ff:fe93:8dde @ eri0:2
traceroute to london (4::114:a00:20ff:ab3d:83ed), 30 hops max, \
60 byte packets
1 frbldg7c-86 (4::56:a00:20ff:fe1f:65a1) 1.786 ms 1.544 ms 1.719 ms
2 frbldg7b-77 (4::255:0:0:c0a8:517) 2.587 ms 3.001 ms 2.988 ms
3 london (4::114:a00:20ff:ab3d:83ed) 3.122 ms 2.744 ms 3.356 ms

The target host, london, has both IPv4 and IPv6 addresses in the name
service database. According to the default behavior, traceroute uses IPv6
address of the destination host.

Example 2: Using the traceroute Utility For a Host Which has Only IPv4


In the following examples, traceroute is tracking the route to host
sanfrancisco, which has only IPv4 addresses in the name service database.
Therefore traceroute uses only IPv4 addresses. The following shows the
7-hop path that a packet would follow from the host istanbul to the host

istanbul% traceroute sanfrancisco
traceroute: Warning: Multiple interfaces found; using @eri0
traceroute to sanfrancisco (, 30 hops max, 40 byte packets
1 frbldg7c-86 ( 1.516 ms 1.283 ms 1.362 ms
2 bldg1a-001 ( 2.277 ms 1.773 ms 2.186 ms
3 bldg4-bldg1 ( 1.978 ms 1.986 ms 13.996 ms
4 bldg6-bldg4 ( 2.655 ms 3.042 ms 2.344 ms
5 ferbldg11a-001 ( 2.636 ms 3.432 ms 3.830 ms
6 frbldg12b-153 ( 3.452 ms 3.146 ms 2.962 ms
7 sanfrancisco ( 3.430 ms 3.312 ms 3.451 ms

Example 3: Using the traceroute Utility With Source Routing

The following example shows the path of a packet that goes from istanbul
to sanfrancisco through the hosts cairo and paris, as specified by the -g
option. The -I option makes traceroute send ICMP ECHO probes to the host
sanfrancisco. The -i options sets the source address to the IP address
configured on the interface qe0.

istanbul% traceroute -g cairo -g paris -i qe0 -q 1 -I sanfrancisco
traceroute to sanfrancisco (, 30 hops max, 56 byte packets
1 frbldg7c-86 ( 2.012 ms
2 flrbldg7u ( 4.960 ms
3 cairo ( 4.894 ms
4 flrbldg7u ( 3.475 ms
5 frbldg7c-017 ( 4.126 ms
6 paris ( 4.086 ms
7 frbldg7b-82 ( 6.454 ms
8 bldg1a-001 ( 6.541 ms
9 bldg6-bldg4 ( 6.518 ms
10 ferbldg11a-001 ( 9.108 ms
11 frbldg12b-153 ( 9.634 ms
12 sanfrancisco ( 14.631 ms


The following exit values are returned:


Successful operation.


An error occurred.


signal(3C), attributes(7), privileges(7), zones(7), netstat(8), ping(8)


This utility is intended for use in network testing, measurement and
management. It should be used primarily for manual fault isolation.
Because of the load it could impose on the network, it is unwise to use
traceroute(8) during normal operations or from automated scripts.

June 13, 2021 TRACEROUTE(8)