-s hostname hw_addr, --set hostname
Manually create an ARP address mapping entry for host hostname
with hardware address set to hw_addr class, but for most classes
one can assume that the usual presentation can be used. For the
Ethernet class, this is 6 bytes in hexadecimal, separated by
colons. When adding proxy arp entries (that is those with the
publish flag set a netmask may be specified to proxy arp for
entire subnets. This is not good practice, but is supported by
older kernels because it can be useful. If the temp flag is not
supplied entries will be permanent stored into the ARP cache.
NOTE: As of kernel 2.2.0 it is no longer possible to set an ARP
entry for an entire subnet. Linux instead does automagic proxy
arp when a route exists and it is forwarding. See arp(7) for
details.