1 .TH ARP 8 "2005-05-16" "net-tools" "Linux Programmer's Manual"
3 arp \- manipulate the system ARP cache
22 .B -s hostname hw_addr
29 .B -s hostname hw_addr
49 manipulates the kernel's ARP cache in various ways. The primary options
50 are clearing an address mapping entry and manually setting up one. For
51 debugging purposes, the
53 program also allows a complete dump of the ARP cache.
57 Tell the user what is going on by being verbose.
60 shows numerical addresses instead of trying to determine symbolic host, port
63 .B "\-H type, \-\-hw-type type"
64 When setting or reading the ARP cache, this optional parameter tells
66 which class of entries it should check for. The default value of
69 (i.e. hardware code 0x01 for IEEE 802.3 10Mbps Ethernet).
70 Other values might include network technologies such as
71 .RB "ARCnet (" arcnet ")"
73 .RB "PROnet (" pronet ")"
75 .RB "AX.25 (" ax25 ")"
77 .RB "NET/ROM (" netrom ")."
79 .B "\-a [hostname], \-\-display [hostname]"
80 Shows the entries of the specified hosts. If the
82 parameter is not used,
84 entries will be displayed.
86 .B "\-d hostname, \-\-delete hostname"
87 Remove any entry for the specified host. This can be used if the
88 indicated host is brought down, for example.
90 .B "\-D, \-\-use-device"
95 .B "\-i If, \-\-device If"
96 Select an interface. When dumping the ARP cache only entries matching
97 the specified interface will be printed. When setting a permanent or
99 ARP entry this interface will be associated with the entry; if this
100 option is not used, the kernel will guess based on the routing
103 entries the specified interface is the interface on which ARP requests will
107 This has to be different from the interface to which the IP
108 datagrams will be routed.
110 .B "\-s hostname hw_addr, \-\-set hostname"
111 Manually create an ARP address mapping entry for host
113 with hardware address set to
115 . The format of the hardware address is dependent on the hardware
116 class, but for most classes one can assume that the usual presentation
117 can be used. For the Ethernet class, this is 6 bytes in hexadecimal,
118 separated by colons. When adding proxy arp entries (that is those with
123 may be specified to proxy arp for entire subnets. This is not good
124 practice, but is supported by older kernels because it can be
127 flag is not supplied entries will be permanent stored into the ARP
131 As of kernel 2.2.0 it is no longer possible to set an ARP entry for an
132 entire subnet. Linux instead does automagic proxy arp when a route
133 exists and it is forwarding. See
135 for details. Also the
137 option which is available for delete and set operations cannot be
138 used with 2.4 and newer kernels.
140 .B "\-f filename, \-\-file filename"
143 option, only this time the address info is taken from file
145 . This can be used if ARP entries for a lot of hosts have to be
146 set up. The name of the data file is very often
148 but this is not official. If no filename is specified /etc/ethers
151 The format of the file is simple; it
152 only contains ASCII text lines with a hostname, and a hardware
153 address separated by whitespace. Additionally the
154 .BR "pub" , " temp" " and" " netmask"
157 In all places where a
159 is expected, one can also enter an
161 in dotted-decimal notation.
163 As a special case for compatibility the order of the hostname and
164 the hardware address can be exchanged.
166 Each complete entry in the ARP cache will be marked with the
168 flag. Permanent entries are marked with
170 and published entries have the
182 rarp(8), route(8), ifconfig(8), netstat(8)
184 Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org> with a lot of improvements
185 from net-tools Maintainer Bernd Eckenfels <net-tools@lina.inka.de>.