arp —
address resolution display and
control
arp |
[-n] [-c
cpu] [-i
interface] hostname |
arp |
[-n] [-c
cpu] [-i
interface] -a |
arp |
-s hostname ether_addr
[temp] [pub
[only]] |
arp |
-S hostname ether_addr
[temp] [pub
[only]] |
The arp utility displays and modifies the
Internet-to-Ethernet address translation tables used by the address resolution
protocol (arp(4)). With no flags, the program displays the current ARP entry for
hostname. The host may be specified by name or by
number, using Internet dot notation.
Available options:
-a- The program displays or deletes all of the current ARP entries.
-c
cpu- On SMP systems the route table is replicated. This option allows the route
table for a specific cpu to be accessed and exists primarily for debugging
purposes.
-d- A super-user may delete an entry for the host called
hostname with the
-d flag.
If the pub keyword is specified, only the
“published” ARP entry for this host will be deleted.
Alternatively, the -d flag may be
combined with the -a flag to delete all
entries.
-i
interface- Limit the operation scope to the ARP entries on
interface. Applicable only to the following
operations: display one, display all, delete all.
-n- Show network addresses as numbers (normally
arp
attempts to display addresses symbolically).
-s
hostname ether_addr- Create an ARP entry for the host called hostname
with the Ethernet address ether_addr. The Ethernet
address is given as six hex bytes separated by colons. The entry will be
permanent unless the word
temp is given in the
command. If the word pub is given, the entry will
be “published”; i.e., this system will act as an ARP server,
responding to requests for hostname even though the
host address is not its own. In this case the
ether_addr can be given as
auto in which case the interfaces on this host
will be examined, and if one of them is found to occupy the same subnet,
its Ethernet address will be used. If the only
keyword is also specified, this will create a “published (proxy
only)” entry. This type of entry is created automatically if
arp detects that a routing table entry for
hostname already exists.
-S
hostname ether_addr- Is just like
-s except any existing ARP entry for
this host will be deleted first.
-f
filename- Cause the file filename to be read and multiple
entries to be set in the ARP tables. Entries in the file should be of the
form
hostname ether_addr
[temp] [pub]
with argument meanings as given above. Leading whitespace and
empty lines are ignored. A ‘#’
character will mark the rest of the line as a comment.
The arp utility appeared in
4.3BSD.