Normally, proxy ARP in FreeBSD is set up on a host-by-host basis using the arp(8) utility, by adding an entry for each host inside a given subnet for which proxying of ARP requests is desired. However, the "proxy all" feature causes the local host to act as a proxy for all hosts reachable through some other network interface, different from the one the request came in from. It may be enabled by setting the sysctl(8) MIB variable net.link.ether.inet.proxyall to 1.
