FPING(8) fping FPING(8)
2025-12-31
NAME
fping - send ICMP ECHO_REQUEST packets to network hosts
SYNOPSIS
fping [ options ] [ systems... ]
DESCRIPTION
fping is a program like ping which uses the Internet Control Message
Protocol (ICMP) echo request to determine if a target host is
responding. fping differs from ping in that you can specify any
number of targets on the command line, or specify a file containing
the lists of targets to ping. Instead of sending to one target until
it times out or replies, fping will send out a ping packet and move on
to the next target in a round-robin fashion. In the default mode, if
a target replies, it is noted and removed from the list of targets to
check; if a target does not respond within a certain time limit and/or
retry limit it is designated as unreachable. fping also supports
sending a specified number of pings to a target, or looping
indefinitely (as in ping ). Unlike ping, fping is meant to be used in
scripts, so its output is designed to be easy to parse. Current
statistics can be obtained without termination of process with signal
SIGQUIT (^\ from the keyboard on most systems).
OPTIONS
-4, --ipv4
Restrict name resolution and IPs to IPv4 addresses.
-6, --ipv6
Restrict name resolution and IPs to IPv6 addresses.
-a, --alive
Show systems that are alive. (Options -c and -C override -a.)
-A, --addr
Display targets by address rather than DNS name. Combined with
-d, the output will be both the ip and (if available) the
hostname.
-b, --size=BYTES
Number of bytes of ping data to send. The minimum size (normally
12) allows room for the data that fping needs to do its work
(sequence number, timestamp). The reported received data size
includes the IP header (normally 20 bytes) and ICMP header (8
bytes), so the minimum total size is 40 bytes. Default is 56, as
in ping. Maximum is the theoretical maximum IP datagram size
(64K), though most systems limit this to a smaller, system-
dependent number. Cannot be used together with --icmp-timestamp.
-B, --backoff=N
Backoff factor. In the default mode, fping sends several requests
to a target before giving up, waiting longer for a reply on each
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successive request. This parameter is the value by which the
wait time (-t) is multiplied on each successive request; it must
be entered as a floating-point number (x.y). The default is 1.5.
-c, --count=N
Number of request packets to send to each target. In this mode,
a line is displayed for each received response (this can
suppressed with -q or -Q). Also, statistics about responses for
each target are displayed when all requests have been sent (or
when interrupted). This option overrides -a or -u.
-C, --vcount=N
Similar to -c, but the per-target statistics are displayed in a
format designed for automated response-time statistics gathering.
For example:
$ fping -C 5 -q somehost
somehost : 91.7 37.0 29.2 - 36.8
shows the response time in milliseconds for each of the five
requests, with the "-" indicating that no response was received
to the fourth request. This option overrides -a or -u.
--check-source
Discard Echo replies that are sourced from a different address
than the target address. This avoids spurious reachability
results on busy monitoring systems where two fping instances with
the same lower 16 bits of the process ID may be running at the
same time.
-d, --rdns
Use DNS to lookup address of ping target. This allows you to give
fping a list of IP addresses as input and print hostnames in the
output. This is similar to option -n/--name, but will force a
reverse-DNS lookup even if you give hostnames as target
(NAME->IP->NAME).
-D, --timestamp
Add Unix timestamps in front of output lines generated with in
looping or counting modes (-l, -c, or -C).
Subcommand: --timestamp-format=ctime|iso|rfc3339
Allow to change the timestamp format of the -D option to the
following format types.
ctime = "%c" (Example: Mon Jun 10 07:50:00 2024)
iso = "%Y-%m-%dT%T%z" (Example: 2024-06-10T07:50:00+0200)
rfc3339 = "%Y-%m-%d %H:%M:%S" (Example: 2024-06-10 07:50:00)
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-e, --elapsed
Show elapsed (round-trip) time of packets.
-f, --file
Read list of targets from a file.
-g, --generate addr/mask
Generate a target list from a supplied IP netmask, or a starting
and ending IP. Specify the netmask or start/end in the targets
portion of the command line. If an IPv4 network with netmask is
given, the network and broadcast addresses will be excluded.
Example: To ping the network 192.168.1.0/24, the specified
command line could look like either:
$ fping -g 192.168.1.0/24
or
$ fping -g 192.168.1.1 192.168.1.254
-h, --help
Print usage message.
-H, --ttl=N
Set the IP TTL field (time to live hops).
--print-ttl
Displays the IPv4 TTL value from the IP Header in the output. If
fping cannot read the TTL value, "(TTL unknown)" is returned.
-i, --interval=MSEC
The minimum amount of time (in milliseconds) between sending a
ping packet to any target (default is 10, minimum is 0 (1 for
non-root users if fping was configured with
"--enable-safe-limits")).
-I, --iface=IFACE
Set the interface (requires SO_BINDTODEVICE support).
--icmp-timestamp
Send ICMP timestamp requests (ICMP type 13) instead of ICMP Echo
requests. Print ICMP timestamps for originate, receive, and
transmit, together with the local receive time in the same
format, in addition to normal output. Cannot be used together
with -b because ICMP timestamp messages have a fixed size. IPv4
only, requires root privileges or cap_net_raw.
-J, --json
Format output JSON (-c, -C, or -l required)
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Example usage:
$ fping -J -c 1 127.0.0.1
or
$ fping -J -s -c 1 -q 127.0.0.1
-k, --fwmark=FWMARK
Set FWMARK on ping packets for policy-based routing. Requires
Linux kernel 2.6.25<=, and root privileges or cap_net_admin.
-l, --loop
Loop sending packets to each target indefinitely. Can be
interrupted with Ctrl-C; statistics about responses for each
target are then displayed.
-m, --all
Send pings to each of a target host's multiple IP addresses (use
of option '-A' is recommended).
-M, --dontfrag
Set the "Don't Fragment" bit in the IP header (used to
determine/test the MTU).
-n, --name
If targets are specified as IP addresses, do a reverse-DNS lookup
on them to print hostnames in the output.
-N, --netdata
Format output for netdata (-l -Q are required). See:
<https://netdata.cloud/>
-o, --outage
Calculate "outage time" based on the number of lost pings and the
interval used (useful for network convergence tests).
-O, --tos=N
Set the typ of service flag (TOS). N can be either decimal or
hexadecimal (0xh) format.
--print-tos
Displays the TOS value in the output. If fping cannot read the
TOS value, "(TOS unknown)" is returned.
-p, --period=MSEC
In looping or counting modes (-l, -c, or -C), this parameter sets
the time in milliseconds that fping waits between successive
packets to an individual target. Default is 1000 and minimum is
0.001 (10 for non-root users if fping was configured with
"--enable-safe-limits").
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-q, --quiet
Quiet. Don't show per-probe results, but only the final summary.
Also don't show ICMP error messages.
-Q, --squiet=SECS[,cumulative]
Like -q, but additionally show interval summary results every
SECS seconds. With cumulative, show summary results since start
instead of for the last interval, unless option -N is used, too.
-r, --retry=N
Retry limit (default 3). This is the number of times an attempt
at pinging a target will be made, not including the first try.
-R, --random
Instead of using all-zeros as the packet data, generate random
bytes. Use to defeat, e.g., link data compression.
-s, --stats
Print cumulative statistics upon exit.
-S, --src=addr
Set source address.
--seqmap-timeout=MSEC
Timeout for sequence number mappings in milliseconds. Sequence
numbers can be reused after the timeout. The default value is
10000ms.
-t, --timeout=MSEC
Initial target timeout in milliseconds. In the default, non-loop
mode, the default timeout is 500ms, and it represents the amount
of time that fping waits for a response to its first request.
Successive timeouts are multiplied by the backoff factor
specified with -B.
In loop/count mode, the default timeout is automatically adjusted
to match the "period" value (but not more than 2000ms). You can
still adjust the timeout value with this option, if you wish to,
but note that setting a value larger than "period" produces
inconsistent results, because the timeout value can be respected
only for the last ping.
Also note that any received replies that are larger than the
timeout value, will be discarded.
-T n Ignored (for compatibility with fping 2.4).
-u, --unreach
Show targets that are unreachable. (Options -c and -C override
-u.)
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-v, --version
Print fping version information.
-x, --reachable=N
Given a list of hosts, this mode checks if number of reachable
hosts is >= N and exits true in that case.
-X, --fast-reachable=N
Given a list of hosts, this mode immediately exits true once N
alive hosts have been found.
EXAMPLES
Generate 20 pings to two hosts in ca. 1 second (i.e. one ping every 50
ms to each host), and report every ping RTT at the end:
$ fping --quiet --interval=1 --vcount=20 --period=50 127.0.0.1 127.0.0.2
AUTHORS
+ Roland J. Schemers III, Stanford University, concept and versions
1.x
+ RL "Bob" Morgan, Stanford University, versions 2.x
+ David Papp, versions 2.3x and up
+ David Schweikert, versions 3.0 and up
fping website: <http://www.fping.org>
DIAGNOSTICS
Exit status is 0 if all the hosts (or the number of hosts specified
with -x or -X) are reachable, 1 if some (or too many with -x or -X)
hosts were unreachable, 2 if any IP addresses were not found, 3 for
invalid command line arguments, and 4 for a system call failure.
RESTRICTIONS
The number of addresses that can be generated using the -g, --generate
option is limited to 131072 (the number of host addresses in one
111-bit IPv6 prefix, two addresses more than the host addresses in one
15-bit IPv4 prefix).
The length of target names read from file or standard input is limited
to 255 bytes.
The minimum interval for sending successive packets to an individual
target set with the -p n option is 0.001 msec.
If fping was configured with "--enable-safe-limits", the following
values are not allowed for non-root users:
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+ -i n, where n < 1 msec
+ -p n, where n < 10 msec
SEE ALSO
ping(8)
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