Provided by: arp-scan_1.10.0-2build2_amd64 
NAME
arp-scan - Send ARP requests to target hosts and display responses
SYNOPSIS
arp-scan [options] [hosts...]
Target hosts must be specified on the command line unless the --file or --localnet option is used.
Targets can be IPv4 addresses or hostnames. You can also use CIDR notation (10.0.0.0/24) (network and
broadcast included), ranges (10.0.0.1-10.0.0.10), and network:mask (10.0.0.0:255.255.255.0).
DESCRIPTION
arp-scan sends ARP request packets to the specified hosts and displays any responses received. The
network interface can be specified with the --interface option. If no interface is specified, arp-scan
will pick the lowest numbered, configured up interface (excluding loopback).
arp-scan uses raw sockets, which requires privileges on some systems:
Linux with POSIX.1e capabilities support using libcap:
arp-scan is capabilities aware. It requires CAP_NET_RAW in the permitted set and only enables that
capability for the required functions. use setcap cap_net_raw+p /path/to/arp-scan to add
CAP_NET_RAW to the permitted set of the arp-scan executable. Capabilities support also makes SUID
root much safer because arp-scan will drop all capabilities except CAP_NET_RAW and will not run
with full root privileges.
BSD and macOS:
You need read/write access to /dev/bpf*
Any operating system:
Running as root or SUID root will work on any OS but other methods are preferable where possible.
ARP only operates on the local network, and cannot be routed. Although the ARP protocol uses IPv4
addresses, it is not an IP protocol and arp-scan can be used on interfaces without an IPv4 address.
One ARP request is sent for each target. If a host does not respond, the request will be re-sent once
more. The number of retries can be changed with the --retry option. Reducing the number of retries will
reduce the scanning time at the risk of missing some results due to packet loss.
You can specify the bandwidth that arp-scan will use with the --bandwidth option. The default is 256000
bits per second. Increasing the bandwidth will reduce scanning time, but setting the bandwidth too high
may cause a high broadcast packet rate. Another way to specify the packet rate is with the --interval
option.
The time for a single-pass scan (i.e. with --retry=1) is:
time=n×i+t+o
Where n is the number of hosts, i is the interval (given with --interval or calculated from --bandwidth),
t is the timeout (specified with --timeout) and o is the overhead time taken to load the target list and
read the MAC/Vendor mapping files. The overhead is normally negligible (typically around 100ms) but can
be reduced further by the --quiet option. For small lists of hosts, the timeout value will dominate, but
for large lists the packet interval is the most important value.
Any part of the ARP request may be modified through the use of the --arpXXX options as shown in the table
below:
┌─────────────────────────────────────────────────────┐
│ ARP Request Packet Options │
├────────┬──────┬──────────┬──────────────────────────┤
│ Field │ Bits │ Option │ Default │
├────────┼──────┼──────────┼──────────────────────────┤
│ ar$hrd │ 16 │ --arphrd │ 1 (ARPHRD_ETHER) │
│ ar$pro │ 16 │ --arppro │ 0x0800 │
│ ar$hln │ 8 │ --arphln │ 6 (ETH_ALEN) │
│ ar$pln │ 8 │ --arppln │ 4 (IPv4) │
│ ar$op │ 16 │ --arpop │ 1 (ARPOP_REQUEST) │
│ ar$sha │ 48 │ --arpsha │ interface h/w address │
│ ar$spa │ 32 │ --arpspa │ interface IPv4 address │
│ ar$tha │ 48 │ --arptha │ 00:00:00:00:00:00 │
│ ar$tpa │ 32 │ None │ target host IPv4 address │
└────────┴──────┴──────────┴──────────────────────────┘
The most common option is --arpspa, which sets the source IPv4 address in the ARP request, allowing the
ARP request to use a different source address from the interface address. This allows the use of arp-scan
on interfaces with no IPv4 address. Note: Setting ar$spa to the target's IP address causes some
operating systems to report an address clash when they receive an ARP request for their own address.
You can also change the values in the Ethernet frame header as shown below:
┌─────────────────────────────────────────────────────────┐
│ Ethernet Header Options │
├────────────────┬──────┬─────────────┬───────────────────┤
│ Field │ Bits │ Option │ Default │
├────────────────┼──────┼─────────────┼───────────────────┤
│ Dest Address │ 48 │ --destaddr │ ff:ff:ff:ff:ff:ff │
│ Source Address │ 48 │ --srcaddr │ interface address │
│ Protocol Type │ 16 │ --prototype │ 0x0806 (ARP) │
└────────────────┴──────┴─────────────┴───────────────────┘
The --destaddr option which sets the destination Ethernet address is the only one that is commonly used.
By default, ARP responses are displayed in the following format:
<IPv4 Address> <MAC Address> <Vendor Details>
Where IPv4 Address is the IP address of the responding target, MAC Address is its link-layer address and
Vendor Details are the vendor details decoded from the hardware address. The output fields are separated
by a single tab character. You can change the output format with the --format option.
The responses are displayed in the order they are received, which can be different from the order the
requests were sent because some hosts may respond quicker than others.
The vendor decoding uses the files ieee-oui.txt and mac-vendor.txt. ieee-oui.txt is generated from the
IEEE MA-L (OUI), MA-M, MA-S (OUI36) and IAB registries. mac-vendor.txt contains additional MAC to Vendor
mappings, and can be used to add custom mappings. get-oui can be used to update ieee-oui.txt with the
latest data from the IEEE registries.
All IPv4 hosts should respond to ARP request packets, including hosts with packet filtering such as
firewalls. This makes arp-scan a useful tool to discover all active IPv4 hosts on the local network.
OPTIONS
Where an option takes a value, that value is specified as a letter in angle brackets. The letter
indicates the type of data that is expected:
<s> Character string.
<i> Decimal integer, or hex if preceeded by 0x e.g. 2048 or 0x800.
<f> Floating point decimal number.
<m> MAC address, e.g. 01:23:45:67:89:ab or 01-23-45-67-89-ab (case insensitive)
<a> IPv4 address e.g. 10.0.0.1
<h> Hex encoded binary data. No leading 0x. (case insensitive).
<x> Something else - see option description.
General Options
--help or -h
Display this usage message and exit.
--verbose or -v
Display verbose progress messages. Can be used than once to increase verbosity. Max=3.
--version or -V
Display program version and exit. Displays the version, license details, libpcap version, and
whether POSIX.1e capability support is included.
--interface=<s> or -I <s>
Use network interface <s>. If this option is not specified, arp-scan will search the system
interface list for the lowest numbered, configured up interface (excluding loopback).
Host Selection
--file=<s> or -f <s>
Read hostnames or addresses from the specified file. One name or address pattern per line. Use
"-" for stdin.
--localnet or -l
Generate addresses from interface configuration. Generates list from interface address and
netmask (network and broadcast included). You cannot use the --file option or give targets on the
command line. Use --interface to specify the interface.
MAC/Vendor Mapping Files
--ouifile=<s> or -O <s>
Use IEEE registry vendor mapping file <s>. Default is ieee-oui.txt in the current directory. If
that is not found /usr/share/arp-scan/ieee-oui.txt is used.
--macfile=<s> or -m <s>
Use custom vendor mapping file <s>. Default is mac-vendor.txt in the current directory. If that
is not found /etc/arp-scan/mac-vendor.txt is used.
Output Format Control
--quiet or -q
Display minimal output for each responding host. Only the IP address and MAC address are
displayed. Reduces memory usage by about 5MB because the vendor mapping files are not used. Only
the ${ip} and ${mac} fields are available for the --format option if --quiet is specified.
--plain or -x
Supress header and footer text. Only display the responding host details. Useful if the output
will be parsed by a script.
--ignoredups or -g
Don't display duplicate packets. By default duplicate packets are flagged with (DUP: n) where n
is the number of times this host has responded.
--rtt or -D
Calculate and display the packet round-trip time. The time is displayed in milliseconds and
fractional microseconds. Makes the ${rtt} field available for --format.
--format=<s> or -F <s>
Specify the output format string. The format is a string that will be output for each responding
host. Host details can be included by inserting references to fields using the syntax
"${field[;width]}". Fields are displayed right- aligned unless the width is negative in which case
left alignment will be used. The following case- insensitive field names are recognised:
IP Host IPv4 address in dotted quad format
Name Host name if --resolve option given
MAC Host MAC address xx:xx:xx:xx:xx:xx
HdrMAC Ethernet source addr if different
Vendor Vendor details string
Padding Padding after ARP packet in hex if nonzero
Framing Framing type if not Ethernet_II
VLAN 802.1Q VLAN ID if present
Proto ARP protocol if not 0x0800
DUP Packet number for duplicate packets (>1)
RTT Round trip time if --rtt option given
Only the ${ip} and ${mac} fields are available if the --quiet option is specified.
Any characters that are not fields are output verbatim. "\" introduces escapes:
\n newline
\r carriage return
\t tab
\ suppress special meaning for following character
You should enclose the --format argument in 'single quotes' to protect special characters from the
shell.
Example: --format='${ip}\t${mac}\t${vendor}'
Host List Randomisation
--random or -R
Randomise the target host list.
--randomseed=<i>
Seed the pseudo random number generator. Useful if you want a reproducible --random order.
Output Timing and Retry
--retry=<i> or -r <i>
Set total number of attempts per host to <i>, default=2.
--backoff=<f> or -b <f>
Set backoff factor to <f>, default=1.50. Multiplies timeout by <f> for each pass.
--timeout=<i> or -t <i>
Set initial per host timeout to <i> ms, default=500. This timeout is for the first packet sent to
each host. subsequent timeouts are multiplied by the backoff factor which is set with --backoff.
--interval=<x> or -i <x>
Set minimum packet interval to <x>. This controls the outgoing bandwidth usage by limiting the
packet rate. If you want to use up to a given bandwidth it is easier to use the --bandwidth option
instead. The interval is in milliseconds, or microseconds if "u" is appended.
--bandwidth=<x> or -B <x>
Set outbound bandwidth to <x>, default=256000. The value is in bits per second. Append K for
kilobits or M for megabits (decimal multiples). You cannot specify both --interval and
--bandwidth.
DNS Resolution
--numeric or -N
Targets must be IP addresses, not hostnames. Can reduce startup time for large target lists.
--resolve or -d
Resolve responding addresses to hostnames. The default output format will display the hostname
instead of the IPv4 address. This option makes the ${name} field available for the --format
option.
Output ARP Packet
--arpsha=<m> or -u <m>
Set the ARP source Ethernet address. Sets the 48-bit ar$sha field but does not change the
hardware address in the frame header, see --srcaddr for how to change that address. Default is the
Ethernet address of the outgoing interface.
--arptha=<m> or -w <m>
Set the ARP target Ethernet address. Sets the 48-bit ar$tha field. The default is zero, because
this field is not used for ARP request packets.
--arphrd=<i> or -H <i>
Set the ARP hardware type, default=1. Sets the 16-bit ar$hrd field. The default is 1
(ARPHRD_ETHER). Many operating systems also respond to 6 (ARPHRD_IEEE802).
--arppro=<i> or -p <i>
Set the ARP protocol type, default=0x0800. Sets the 16-bit ar$pro field. Most operating systems
only respond to 0x0800 (IPv4).
--arphln=<i> or -a <i>
Set the hardware address length, default=6. Sets the 8-bit ar$hln field. The lengths of the
ar$sha and ar$tha fields are not changed by this option; it only changes the ar$hln field.
--arppln=<i> or -P <i>
Set the protocol address length, default=4. Sets the 8-bit ar$pln field. The lengths of the
ar$spa and ar$tpa fields are not changed by this option; it only changes the ar$pln field.
--arpop=<i> or -o <i>
Specify the ARP operation, default=1. Sets the 16-bit ar$op field. Most operating systems only
respond to the value 1 (ARPOP_REQUEST).
--arpspa=<a> or -s <a>
Set the source IPv4 address. The address should be in dotted quad format, or the string "dest"
which sets the source address to the target host address. The default is the outgoing interface
address. Sets the 32-bit ar$spa field. Some operating systems only respond if the source address
is within the network of the receiving interface. Setting ar$spa to the destination IP address
can cause some operating systems to report an address clash.
Output Ethernet Header
--srcaddr=<m> or -S <m>
Set the source Ethernet MAC address. Default is the interface MAC address. This sets the address
in the Ethernet header. It does not change the address in the ARP packet: use --arpsha to change
that address.
--destaddr=<m> or -T <m>
Set the destination MAC address. Sets the destination address in the Ethernet header. Default is
ff:ff:ff:ff:ff:ff (broadcast) Hosts also respond if the request is sent to their unicast address,
or to a multicast address they are listening on.
--prototype=<i> or -y <i>
Sets the Ethernet protocol type, default=0x0806. This sets the protocol type field in the
Ethernet header.
--llc or -L
Use RFC 1042 LLC/SNAP encapsulation for 802.2 networks. arp-scan will decode and display ARP
responses in both Ethernet-II and IEEE 802.2 formats irrespective of this option.
--vlan=<i> or -Q <i>
Use 802.1Q tagging with VLAN id <i>. The id should be in the range 0 to 4095. arp-scan will
decode and display ARP responses in 802.1Q format irrespective of this option.
Misc Options
--limit=<i> or -M <i>
Exit after the specified number of hosts have responded. arp-scan will exit with status 1 if the
number of responding hosts is less than the limit. Can be used in scripts to check if fewer hosts
respond without having to parse the output.
--pcapsavefile=<s> or -W <s>
Write received packets to pcap savefile <s>. ARP responses will be written to the specified file
as well as being decoded and displayed.
--snap=<i> or -n <i>
Set the pcap snap length to <i>. Default=64. Specifies the frame capture length, including the
Ethernet header. The default is normally sufficient.
--retry-send=<i> or -Y <i>
Set number of send attempts, default=20.
--retry-send-interval=<i> or -E <i>
Set interval between send attempts. Interval is in milliseconds or microseconds if "u" is
appended. default=5.
--padding=<h> or -A <h>
Specify padding after packet data. Set padding after the ARP request to hex value <h>.
EXIT STATUS
arp-scan will exit with 0 on successful completion or >0 if an error was encountered.
If the --limit option is specified, arp-scan will also exit with a non-zero exit code if the number of
responding hosts is less than the specified limit.
FILES
/usr/share/arp-scan/ieee-oui.txt
List of IEEE OUI (Organisationally Unique Identifier) to vendor mappings.
/etc/arp-scan/mac-vendor.txt
List of other Ethernet MAC to vendor mappings, including local additions.
EXAMPLES
Simple Scan
Scan the default network using the interface IPv4 configuration to generate the list of hosts to scan.
$ arp-scan --localnet
Interface: eth0, type: EN10MB, MAC: 50:65:f3:f0:6d:7c, IPv4: 10.0.0.106
Starting arp-scan 1.9.9 with 256 hosts (https://github.com/royhills/arp-scan)
10.0.0.14 a4:1f:72:7f:25:bb Dell Inc.
10.0.0.22 10:60:4b:73:43:de Hewlett Packard
10.0.0.74 00:0c:29:90:07:e9 VMware, Inc.
10.0.0.75 00:0c:29:66:9e:c2 VMware, Inc.
10.0.0.76 00:0c:29:d0:e1:ea VMware, Inc.
10.0.0.82 9c:b6:54:bb:f3:ec Hewlett Packard
10.0.0.84 00:21:9b:fd:b9:b3 Dell Inc.
10.0.0.85 00:02:b3:eb:5a:f8 Intel Corporation
10.0.0.91 00:9c:02:a5:7b:29 Hewlett Packard
10.0.0.92 d4:ae:52:d0:07:6f Dell Inc.
10.0.0.93 d4:ae:52:d0:04:9b Dell Inc.
10.0.0.96 9c:b6:54:bb:f5:35 Hewlett Packard
10.0.0.97 00:0c:29:0e:95:20 VMware, Inc.
10.0.0.104 50:65:f3:f0:70:a4 Hewlett Packard
15 packets received by filter, 0 packets dropped by kernel
Ending arp-scan 1.9.9: 256 hosts scanned in 1.532 seconds (167.10 hosts/sec). 14 responded
Output Formatting
Scan all hosts in 10.0.0.0/24 using interface eth0. Calculate round-trip time and display in aligned
columns using a custom format.
$ arp-scan -I eth0 --rtt --format='|${ip;-15}|${mac}|${rtt;8}|' 10.0.0.0/24
Interface: eth0, type: EN10MB, MAC: 50:65:f3:f0:6d:7c, IPv4: 10.0.0.106
Starting arp-scan 1.9.9 with 256 hosts (https://github.com/royhills/arp-scan)
|10.0.0.14 |a4:1f:72:7f:25:bb| 0.280|
|10.0.0.22 |10:60:4b:73:43:de| 0.293|
|10.0.0.74 |00:0c:29:90:07:e9| 0.380|
|10.0.0.75 |00:0c:29:66:9e:c2| 0.311|
|10.0.0.76 |00:0c:29:d0:e1:ea| 0.326|
|10.0.0.82 |9c:b6:54:bb:f3:ec| 0.216|
|10.0.0.84 |00:21:9b:fd:b9:b3| 0.244|
|10.0.0.85 |00:02:b3:eb:5a:f8| 0.244|
|10.0.0.91 |00:9c:02:a5:7b:29| 0.209|
|10.0.0.92 |d4:ae:52:d0:07:6f| 0.289|
|10.0.0.93 |d4:ae:52:d0:04:9b| 0.278|
|10.0.0.96 |9c:b6:54:bb:f5:35| 0.255|
|10.0.0.97 |00:0c:29:0e:95:20| 0.288|
|10.0.0.104 |50:65:f3:f0:70:a4| 0.263|
14 packets received by filter, 0 packets dropped by kernel
Ending arp-scan 1.9.9: 256 hosts scanned in 2.032 seconds (125.98 hosts/sec). 14 responded
CSV Output
--plain removes extraneous output.
$ arp-scan -I eth0 --plain --format='${ip},${mac},"${vendor}"' 10.0.0.0/24
10.0.0.14,a4:1f:72:7f:25:bb,"Dell Inc."
10.0.0.22,10:60:4b:73:43:de,"Hewlett Packard"
10.0.0.74,00:0c:29:90:07:e9,"VMware, Inc."
10.0.0.75,00:0c:29:66:9e:c2,"VMware, Inc."
10.0.0.76,00:0c:29:d0:e1:ea,"VMware, Inc."
10.0.0.82,9c:b6:54:bb:f3:ec,"Hewlett Packard"
10.0.0.84,00:21:9b:fd:b9:b3,"Dell Inc."
10.0.0.85,00:02:b3:eb:5a:f8,"Intel Corporation"
10.0.0.91,00:9c:02:a5:7b:29,"Hewlett Packard"
10.0.0.92,d4:ae:52:d0:07:6f,"Dell Inc."
10.0.0.93,d4:ae:52:d0:04:9b,"Dell Inc."
10.0.0.96,9c:b6:54:bb:f5:35,"Hewlett Packard"
10.0.0.97,00:0c:29:0e:95:20,"VMware, Inc."
10.0.0.104,50:65:f3:f0:70:a4,"Hewlett Packard"
SEE ALSO
get-oui(1)
arp-fingerprint(1)
http://www.royhills.co.uk/wiki/ The arp-scan wiki page.
https://github.com/royhills/arp-scan The arp-scan homepage.
November 9, 2022 ARP-SCAN(1)