1ARP(8) Linux Programmer's Manual ARP(8)
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6 arp - manipulate the system ARP cache
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10 arp [-evn] [-H type] [-i if] -a [hostname]
11 arp [-v] [-i if] -d hostname [pub]
13 arp [-v] [-H type] [-i if] -s hostname hw_addr [temp]
15 arp [-v] [-H type] [-i if] -s hostname hw_addr [netmask nm] pub
17 arp [-v] [-H type] [-i if] -Ds hostname ifa [netmask nm] pub
19 arp [-vnD] [-H type] [-i if] -f [filename]
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24 This program is obsolete. For replacement check ip neighbor.
25
28 Arp manipulates the kernel's ARP cache in various ways. The primary
29 options are clearing an address mapping entry and manually setting up
30 one. For debugging purposes, the arp program also allows a complete
31 dump of the ARP cache.
32
35 -v, --verbose
36 Tell the user what is going on by being verbose.
37 -n, --numeric
39 shows numerical addresses instead of trying to determine sym‐
40 bolic host, port or user names.
41 -H type, --hw-type type, -t type
43 When setting or reading the ARP cache, this optional parameter
44 tells arp which class of entries it should check for. The
45 default value of this parameter is ether (i.e. hardware code
46 0x01 for IEEE 802.3 10Mbps Ethernet). Other values might
47 include network technologies such as ARCnet (arcnet) , PROnet
48 (pronet) , AX.25 (ax25) and NET/ROM (netrom).
49 -a [hostname], --all [hostname]
51 Shows the entries of the specified hosts. If the hostname
52 parameter is not used, all entries will be displayed. The
53 entries will be displayed in alternate (BSD) style.
54 -d hostname, --delete hostname
56 Remove any entry for the specified host. This can be used if
57 the indicated host is brought down, for example.
58 -D, --use-device
60 Use the interface ifa's hardware address.
61 -e Shows the entries in default (Linux) style.
63 -i If, --device If
65 Select an interface. When dumping the ARP cache only entries
66 matching the specified interface will be printed. When setting a
67 permanent or temp ARP entry this interface will be associated
68 with the entry; if this option is not used, the kernel will
69 guess based on the routing table. For pub entries the specified
70 interface is the interface on which ARP requests will be
71 answered.
72 NOTE: This has to be different from the interface to which the
74 IP datagrams will be routed.
75 -s hostname hw_addr, --set hostname
77 Manually create an ARP address mapping entry for host hostname
78 with hardware address set to hw_addr class, but for most classes
79 one can assume that the usual presentation can be used. For the
80 Ethernet class, this is 6 bytes in hexadecimal, separated by
81 colons. When adding proxy arp entries (that is those with the
82 publish flag set a netmask may be specified to proxy arp for
83 entire subnets. This is not good practice, but is supported by
84 older kernels because it can be useful. If the temp flag is not
85 supplied entries will be permanent stored into the ARP cache.
86 NOTE: As of kernel 2.2.0 it is no longer possible to set an ARP
87 entry for an entire subnet. Linux instead does automagic proxy
88 arp when a route exists and it is forwarding. See arp(7) for
89 details.
90 -f filename, --file filename
92 Similar to the -s option, only this time the address info is
93 taken from file filename set up. The name of the data file is
94 very often /etc/ethers, but this is not official. If no filename
95 is specified /etc/ethers is used as default.
96 The format of the file is simple; it only contains ASCII text
98 lines with a hardware address and a hostname separated by white‐
99 space. Additionally the pub, temp and netmask flags can be used.
100 In all places where a hostname is expected, one can also enter an IP
102 address in dotted-decimal notation.
103 As a special case for compatibility the order of the hostname and the
105 hardware address can be exchanged.
106 Each complete entry in the ARP cache will be marked with the C flag.
108 Permanent entries are marked with M and published entries have the P
109 flag.
110
113 /proc/net/arp,
114 /etc/networks
115 /etc/hosts
116 /etc/ethers
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120 ip(8)
121
124 Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org> with a lot of improve‐
125 ments from net-tools Maintainer Bernd Eckenfels <net-
126 tools@lina.inka.de>.
127net-tools 5 Jan 1999 ARP(8)