Linux "arp" Command Line Options and Examples
manipulate the system ARP cache

Arp manipulates or displays the kernel's IPv4 network neighbour cache. It can add entries to the table, delete one or display the current content. ARP stands for Address Resolution Protocol, which is used to find the media access control address of a network neighbour for a given IPv4 Address.


arp [-vn] [-H type] [-i if] [-ae] [hostname]

Command Line Options:

Tell the user what is going on by being verbose.
arp -v ...
shows numerical addresses instead of trying to determine symbolic host, port or user names.
arp -n ...
When setting or reading the ARP cache, this optional parameter tells arp which class of entries it should check for. Thedefault value of this parameter is ether (i.e. hardware code 0x01 for IEEE 802.3 10Mbps Ethernet). Other values might includenetwork technologies such as ARCnet (arcnet) , PROnet (pronet) , AX.25 (ax25) and NET/ROM (netrom).
arp -H ...
Use alternate BSD style output format (with no fixed columns).
arp -a ...
Use default Linux style output format (with fixed columns).
arp -e ...
Instead of a hw_addr, the given argument is the name of an interface. arp will use the MAC address of that interface for thetable entry. This is usually the best option to set up a proxy ARP entry to yourself.
arp -D ...
Select an interface. When dumping the ARP cache only entries matching the specified interface will be printed. When setting apermanent or temp ARP entry this interface will be associated with the entry; if this option is not used, the kernel willguess based on the routing table. For pub entries the specified interface is the interface on which ARP requests will beanswered.NOTE: This has to be different from the interface to which the IP datagrams will be routed. NOTE: As of kernel 2.2.0 it is nolonger possible to set an ARP entry for an entire subnet. Linux instead does automagic proxy arp when a route exists and it isforwarding. See arp(7) for details. Also the dontpub option which is available for delete and set operations cannot be usedwith 2.4 and newer kernels.
arp -i ...
Similar to the -s option, only this time the address info is taken from file filename. This can be used if ARP entries for alot of hosts have to be set up. The name of the data file is very often /etc/ethers, but this is not official. If no filenameis specified /etc/ethers is used as default.The format of the file is simple; it only contains ASCII text lines with a hostname, and a hardware address separated bywhitespace. Additionally the pub, temp and netmask flags can be used.In all places where a hostname is expected, one can also enter an IP address in dotted-decimal notation.As a special case for compatibility the order of the hostname and the hardware address can be exchanged.Each complete entry in the ARP cache will be marked with the C flag. Permanent entries are marked with M and published entries havethe P flag.EXAMPLES/usr/sbin/arp -i eth0 -Ds eth1 pubThis will answer ARP requests for on eth0 with the MAC address for eth1./usr/sbin/arp -i eth1 -d the ARP table entry for on interface eth1. This will match published proxy ARP entries and permanent entries.FILES/proc/net/arp/etc/networks/etc/hosts/etc/ethers
arp -f ...