Provided by: 2ping_4.5-1.2_all 
NAME
2ping - A bi-directional ping utility
SYNOPSIS
2ping [options] --listen | host/IP [host/IP [...]]
DESCRIPTION
2ping is a bi-directional ping utility. It uses 3-way pings (akin to TCP SYN, SYN/ACK, ACK) and af‐
ter-the-fact state comparison between a 2ping listener and a 2ping client to determine which direction
packet loss occurs.
To use 2ping, start a listener on a known stable network host. The relative network stability of the
2ping listener host should not be in question, because while 2ping can determine whether packet loss is
occurring inbound or outbound relative to an endpoint, that will not help you determine the cause if both
of the endpoints are in question.
Once the listener is started, start 2ping in client mode and tell it to connect to the listener. The
ends will begin pinging each other and displaying network statistics. If packet loss occurs, 2ping will
wait a few seconds (default 10, configurable with --inquire-wait) before comparing notes between the two
endpoints to determine which direction the packet loss is occurring.
To quit 2ping on the client or listener ends, enter ^C, and a list of statistics will be displayed. To
get a short inline display of statistics without quitting, enter ^\ or send the process a QUIT signal.
OPTIONS
ping-compatible options (long option names are 2ping-specific):
--audible, -a
Audible ping.
--adaptive, -A
Adaptive ping. Interpacket interval adapts to round-trip time, so that effectively not more than
one (or more, if preload is set) unanswered probe is present in the network. On networks with low
rtt this mode is essentially equivalent to flood mode.
--count=count, -c count
Stop after sending count ping requests.
--flood, -f
Flood ping. For every ping sent a period “.” is printed, while for ever ping received a backspace
is printed. This provides a rapid display of how many pings are being dropped. If interval is
not given, it sets interval to zero and outputs pings as fast as they come back or one hundred
times per second, whichever is more.
2ping-specific notes: Detected outbound/inbound loss responses are printed as “>” and “<”, respec‐
tively. Receive errors are printed as “E”. Due to the asynchronous nature of 2ping, successful
responses (backspaces) may overwrite these loss and error characters.
--interval=interval, -i interval
Wait interval seconds between sending each ping. The default is to wait for one second between
each ping normally, or not to wait in flood mode.
--interface-address=address, -I address
Set source IP address. When in listener mode, this option may be specified multiple to bind to
multiple IP addresses. When in client mode, this option may only be specified once, and all out‐
bound pings will be bound to this source IP.
2ping-specific notes: This option only takes an IP address, not a device name. Note that in lis‐
tener mode, if the machine has an interface with multiple IP addresses and an request comes in via
a sub IP, the reply still leaves via the interface’s main IP. So either this option – or (pre‐
ferred) listening on all IPs individually via the Python “netifaces” module – must be used if you
would like to respond via an interface’s sub-IP.
--preload=count, -l count
If specified, 2ping sends that many packets not waiting for reply.
--pattern=hex_bytes, -p hex_bytes
You may specify up to 16 “pad” bytes to fill out the packets you send. This is useful for diag‐
nosing data-dependent problems in a network. For example, --pattern=ff will cause the sent packet
pad area to be filled with all ones.
2ping-specific notes: This pads the portion of the packet that does not contain the active payload
data. If the active payload data is larger than the minimum packet size (--min-packet-size), no
padding will be sent.
--quiet, -q
Quiet output. Nothing is displayed except the summary lines at startup time and when finished.
--packetsize-compat=bytes, -s bytes
ping compatibility; this will set --min-packet-size to this plus 8 bytes.
--verbose, -v
Verbose output. In 2ping, this prints decodes of packets that are sent and received.
--version, -V
Show version and exit.
--deadline=seconds, -w seconds
Specify a timeout, in seconds, before 2ping exits regardless of how many pings have been sent or
received. Due to blocking, this may occur up to one second after the deadline specified.
2ping-specific options:
--help, -h
Print a synposis and exit.
--ipv4, -4
Limit binds to IPv4. In client mode, this forces resolution of dual-homed hostnames to the IPv4
address. (Without --ipv4 or --ipv6, the first result will be used as specified by your operating
system, usually the AAAA address on IPv6-routable machines, or the A address on IPv4-only ma‐
chines.) In listener mode, this filters out any non-IPv4 --interface-address binds, either through
hostname resolution or explicit passing.
--ipv6, -6
Limit binds to IPv6. In client mode, this forces resolution of dual-homed hostnames to the IPv6
address. (Without -4 or -6, the first result will be used as specified by your operating system,
usually the AAAA address on IPv6-routable machines, or the A address on IPv4-only machines.) In
listener mode, this filters out any non-IPv6 --interface-address binds, either through hostname
resolution or explicit passing.
--all-interfaces
Deprecated. In listener mode, all addresses will be listened to by default if the Python “neti‐
faces” module is installed, unless overridden by one or more --interface-address invocations.
--auth=key
Set a shared key, send cryptographic hashes with each packet, and require cryptographic hashes
from peer packets signed with the same shared key.
--auth-digest=digest
When --auth is used, specify the digest type to compute the cryptographic hash. Valid options are
hmac-md5 (default), hmac-sha1, hmac-sha256 and hmac-sha512.
--debug
Print (lots of) debugging information.
--encrypt=key
Set a shared key, encrypt 2ping packets, and require encrypted packets from peers encrypted with
the same shared key. Requires the PyCryptodome or PyCrypto module.
--encrypt-method=method
When --encrypt is used, specify the method used to encrypt packets. Valid options are
hkdf-aes256-cbc (default).
--fuzz=percent
Simulate corruption of incoming packets, with a percent probability each bit will be flipped. Af‐
ter fuzzing, the packet checksum will be recalculated, and then the checksum itself will be fuzzed
(but at a lower probability).
--inquire-wait=secs
Wait at least secs seconds before inquiring about a lost packet. Default is 10 seconds. UDP
packets can arrive delayed or out of order, so it is best to give it some time before inquiring
about a lost packet.
--listen
Start as a listener. The listener will not send out ping requests at regular intervals, and will
instead wait for the far end to initiate ping requests. A listener is required as the remote end
for a client. When run as a listener, a SIGHUP will reload the configuration on all interfaces.
--loopback
Use one or more client/listener pairs of UNIX datagram sockets. Mainly for testing purposes.
--loopback-pairs=pairs
Number of pairs to generate when using --loopback.
--min-packet-size=min
Set the minimum total payload size to min bytes, default 128. If the payload is smaller than min
bytes, padding will be added to the end of the packet.
--max-packet-size=max
Set the maximum total payload size to max bytes, default 512, absolute minimum 64. If the payload
is larger than max bytes, information will be rearranged and sent in future packets when possible.
--nagios=wrta,wloss%,crta,closs%
Produce output suitable for use in a Nagios check. If --count is not specified, defaults to 5
pings. A warning condition (exit code 1) will be returned if average RTT exceeds wrta or ping
loss exceeds wloss%. A critical condition (exit code 2) will be returned if average RTT exceeds
crta or ping loss exceeds closs%.
--no-3way
Do not perform 3-way pings. Used most often when combined with --listen, as the listener is usu‐
ally the one to determine whether a ping reply should become a 3-way ping.
Strictly speaking, a 3-way ping is not necessary for determining directional packet loss between
the client and the listener. However, the extra leg of the 3-way ping allows for extra chances to
determine packet loss more efficiently. Also, with 3-way ping disabled, the listener will receive
no client performance indicators, nor will the listener be able to determine directional packet
loss that it detects.
--no-match-packet-size
When sending replies, 2ping will try to match the packet size of the received packet by adding
padding if necessary, but will not exceed --max-packet-size. --no-match-packet-size disables this
behavior, always setting the minimum to --min-packet-size.
--no-send-version
Do not send the current running version of 2ping with each packet.
--notice=text
Send arbitrary notice text with each packet. If the remote peer supports it, this may be dis‐
played to the user.
--packet-loss=out:in
Simulate random packet loss outbound and inbound. For example, 25:10 means a 25% chance of not
sending a packet, and a 10% chance of ignoring a received packet. A single number without colon
separation means use the same percentage for both outbound and inbound.
--port=port
Use UDP port port, either a numeric port number or a service name string. With --listen, this is
the port to bind as, otherwise this is the port to send to. Default is UDP port 15998.
When port “-1” is specified, a random unused high port is picked. This is useful for automated
unit and functional testing, but not for normal use.
--send-monotonic-clock
Send a monotonic clock value with each packet. Peer time (if sent by the peer) can be viewed with
--verbose.
--send-random=bytes
Send random data to the peer, up to bytes. The number of bytes will be limited by other factors,
up to --max-packet-size. If this data is to be used for trusted purposes, it should be combined
with --auth for HMAC authentication.
--send-time
Send the host time (wall clock) with each packet. Peer time (if sent by the peer) can be viewed
with --verbose.
--srv In client mode, causes hostnames to be looked up via DNS SRV records. If the SRV query returns
multiple record targets, they will all be pinged in parallel; priority and weight are not consid‐
ered. The record’s port will be used instead of --port. This functionality requires the
dnspython module to be installed.
--srv-service=service
When combined with --srv, service name to be used for SRV lookups. Default service is “2ping”.
--stats=interval
Print a line of brief current statistics every interval seconds. The same line can be printed on
demand by entering ^\ or sending the QUIT signal to the 2ping process.
--subtract-peer-host-latency
If a peer sends its host latency (the amount of time it spends between receiving a packet and
sending out a reply), subtract it from RTT calculations.
BUGS
None known, many assumed.
AUTHOR
2ping was written by Ryan Finnie <ryan@finnie.org>.
AUTHORS
Ryan Finnie.
2PING(1)