FPING(8)

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 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)

-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)

    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").

-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.)

-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:

•   -i n, where n < 1 msec

•   -p n, where n < 10 msec

SEE ALSO
ping(8)