Manual: mtr-packet
MTR-PACKET(8) System Administration MTR-PACKET(8)
NAME
mtr-packet - send and receive network probes
DESCRIPTION
mtr-packet is a tool for sending network probes to measure network connectivity and performance. Many network probes
can be sent simultaneously by a single process instance of mtr-packet and additional probes can be generated by an
instance of mtr-packet which already has network probes in flight. It is intended to be used by programs which in‐
voke it with Unix pipes attached to its standard input and output streams.
mtr-packet reads command requests from stdin, each separated by a newline character, and responds with command
replies to stdout, also each separated by a newline character. The syntactic structure of requests and replies are
the same. The following format is used:
TOKEN COMMAND [ARGUMENT-NAME ARGUMENT-VALUE ...]
TOKEN is a unique integer value. The same value will be used as the TOKEN for the response. This is necessary for
associating replies with requests, as commands may be completed in a different order than they are requested. The
invoker of mtr-packet should always use the TOKEN value to determine which command request has completed.
COMMAND is a string identifying the command request type. A common command is send-probe, which will transmit one
network probe.
ARGUMENT-NAME strings and ARGUMENT-VALUE strings always come in pairs. It is a syntactic error to provide an ARGU‐
MENT-NAME without a corresponding ARGUMENT-VALUE. Valid ARGUMENT-NAME strings depend on the COMMAND being used.
REQUESTS
send-probe
Send a network probe to a particular IP address. Either an ip-4 or ip-6 argument must be provided. A valid
send-probe command will reply with reply, no-reply, or ttl-expired.
The following arguments may be used:
ip-4 IP-ADDRESS
The Internet Protocol version 4 address to probe.
ip-6 IP-ADDRESS
The Internet Protocol version 6 address to probe.
protocol PROTOCOL
The protocol to use for the network probe. icmp, sctp, tcp, and udp may be used. The default protocol
is icmp.
port PORT-NUMBER
The destination port to use for sctp, tcp, or udp probes.
local-ip-4 IP-ADDRESS
The local Internet Protocol version 4 address to use when sending probes.
local-ip-6 IP-ADDRESS
The local Internet Protocol version 6 address to use when sending probes.
local-port PORT-NUMBER
For udp probes, the local port number from which to send probes.
timeout TIMEOUT-SECONDS
The number of seconds to wait for a response to the probe before discarding the probe as lost, and gen‐
erating a no-reply command reply.
ttl TIME-TO-LIVE
The time-to-live value for the Internet Protocol packet header used in constructing the probe. This
value determines the number of network hops through which the probe will travel before a response is
generated by an intermediate network host.
size PACKET-SIZE
The size of the packet used to send the probe, in bytes, including the Internet Protocol header and
transport protocol header.
bit-pattern PATTERN-VALUE
The packet payload is filled with bytes of the value specified. Valid pattern values are in the range
0 through 255.
tos TYPE-OF-SERVICE
In the case of IPv4, the "type of service" field in the IP header is set to this value. In the case of
IPv6, the "traffic class" field is set.
mark ROUTING-MARK
The packet mark value to be used by mark-based routing. (Available only on Linux.)
check-support
Check for support for a particular feature in this version of mtr-packet and in this particular operating en‐
vironment. check-support will reply with feature-supported. A feature argument is required.
feature FEATURE-NAME
The name of a feature requested.
Some features which can be checked are send-probe, ip-4, ip-6, icmp, sctp, tcp, udp, and mark. The feature
version can be checked to retrieve the version of mtr-packet.
REPLIES
reply The destination host received the send-probe probe and replied. Arguments of reply are:
ip-4 IP-ADDRESS
The Internet Protocol version 4 address of the host which replied to the probe.
ip-6 IP-ADDRESS
The Internet Protocol version 6 address of the host which replied to the probe.
round-trip-time TIME
The time which passed between the transmission of the probe and its response. The time is provided as
a integral number of microseconds elapsed.
no-reply
No response to the probe request was received before the timeout expired.
ttl-expired
The time-to-live value of the transmitted probe expired before the probe arrived at its intended destination.
Arguments of ttl-expired are:
ip-4 IP-ADDRESS
The Internet Protocol version 4 address of the host at which the time-to-live value expired.
ip-6 IP-ADDRESS
The Internet Protocol version 6 address of the host at which the time-to-live value expired.
round-trip-time TIME
The time which passed between the transmission of the probe and its response. The time is provided as
a integral number of microseconds elapsed.
mpls MPLS-LABEL-LIST
A list of Multiprotocol Label Switching values returned with the probe response. If the mpls argument
is present, one or more MPLS labels will be represented by a comma separated list of values. The val‐
ues are provided in groups of four. The first four values in the list correspond to the first MPLS la‐
bel, the next four values correspond to the second MPLS label, and so on. The values are provided in
this order: label, traffic-class, bottom-of-stack, ttl.
no-route
There was no route to the host used in a send-probe request.
network-down
A probe could not be sent because the network is down.
probes-exhausted
A probe could not be sent because there are already too many unresolved probes in flight.
permission-denied
The operating system denied permission to send the probe with the specified options.
invalid-argument
The command request contained arguments which are invalid.
feature-support
A reply to provided to check-support indicating the availability of a particular feature. The argument pro‐
vided is:
support PRESENT
In most cases, the PRESENT value will be either ok, indicating the feature is supported, or no, indi‐
cating no support for the feature.
In the case that version is the requested FEATURE-NAME, the version of mtr-packet is provided as the
PRESENT value.
EXAMPLES
A controlling program may start mtr-packet as a child process and issue the following command on stdin:
42 send-probe ip-4 127.0.0.1
This will send a network probe to the loopback interface. When the probe completes, mtr-packet will provide a re‐
sponse on stdout such as the following:
42 reply ip-4 127.0.0.1 round-trip-time 126
This indicates that the loopback address replied to the probe, and the round-trip time of the probe was 126 microsec‐
onds.
In order to trace the route to a remote host, multiple send-probe commands, each with a different ttl value, are
used.
11 send-probe ip-4 8.8.8.8 ttl 1
12 send-probe ip-4 8.8.8.8 ttl 2
13 send-probe ip-4 8.8.8.8 ttl 3
...
Each intermediate host would respond with a ttl-expired message, and the destination host would respond with a reply:
11 ttl-expired ip-4 192.168.254.254 round-trip-time 1634
12 ttl-expired ip-4 184.19.243.240 round-trip-time 7609
13 ttl-expired ip-4 172.76.20.169 round-trip-time 8643
14 ttl-expired ip-4 74.40.1.101 round-trip-time 9755
15 ttl-expired ip-4 74.40.5.126 round-trip-time 10695
17 ttl-expired ip-4 108.170.245.97 round-trip-time 14077
16 ttl-expired ip-4 74.40.26.131 round-trip-time 15253
18 ttl-expired ip-4 209.85.245.101 round-trip-time 17080
19 reply ip-4 8.8.8.8 round-trip-time 17039
Note that the replies in this example are printed out of order. (The reply to probe 17 arrives prior to the reply to
probe 16.) This is the reason that it is important to send commands with unique token values, and to use those token
values to match replies with their originating commands.
LANGUAGE BINDINGS
A Python 3.x package for sending asynchronous network probes using mtr-packet is available. See https://pypi.org/
project/mtrpacket/
CONTACT INFORMATION
For the latest version, see the mtr web page at http://www.bitwizard.nl/mtr/
For patches, bug reports, or feature requests, please open an issue on GitHub at: https://github.com/traviscross/mtr.
SEE ALSO
mtr(8), icmp(7), tcp(7), udp(7), TCP/IP Illustrated (Stevens, ISBN 0201633469).
mtr-packet 0.95 MTR-PACKET(8)