Section: Maintenance Commands (8)
Updated: 28 June, 2007
arpd - userspace arp daemon.
Usage: arpd [ -lkh? ] [ -a N ] [ -b dbase ] [ -B number ] [ -f file ] [-p interval ] [ -n time ] [ -R rate ] [ <INTERFACES> ]
The arpd daemon collects gratuitous ARP information, saving it on local disk and feeding it to the kernel on demand to avoid redundant broadcasting due to limited size of the kernel ARP cache.
<INTERFACES> is a list of names of networking interfaces to watch. If no interfaces are given, arpd monitors all the interfaces. In this case arpd does not adjust sysctl parameters, it is assumed that the user does this himself after arpd is started.
:When arpd receives a SIGINT or SIGTERM signal, it exits gracefully, syncing the database and restoring adjusted sysctl parameters. On a SIGHUP it syncs the database to disk. With SIGUSR1 it sends some statistics to syslog. The effect of any other signals is undefined. In particular, they may corrupt the database and leave the sysctl parameters in an unpredictable state.
:In order for arpd to be able to serve as ARP resolver, the kernel must be compiled with the option CONFIG_ARPD and, in the case when interface list in not given on command line, variable app_solicit on interfaces of interest should be in /proc/sys/net/ipv4/neigh/*. If this is not made arpd still collects gratuitous ARP information in its database.
This is the mode in which arpd normally is supposed to work. It is not the default to prevent occasional enabling of too aggressive a mode.
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