*BASH User Commands Ubuntu 10.04.4 LTS Server coreutils
ARPD(8)                                                                ARPD(8)

       arpd - userspace arp daemon.

       Usage: arpd [ -lk ] [ -a N ] [ -b dbase ] [ -f file ] [ interfaces ]

       The arpd daemon collects gratuitous ARP information, saving it on local
       disk and feeding it to kernel on demand to avoid redundant broadcasting
       due to limited size of kernel ARP cache.

       -h -?  Print help

       -l     Dump  arpd database to stdout and exit. Output consists of three
              columns: interface index, IP address and MAC  address.  Negative
              entries  for dead hosts are also shown, in this case MAC address
              is replaced by word FAILED followed by colon and time  when  the
              fact that host is dead was proven the last time.

       -f <FILE>
              Read  and  load  arpd  database from FILE in text format similar
              dumped by option -l. Exit after load, probably listing resulting
              database,  if  option  -l  is also given. If FILE is -, stdin is
              read to get ARP table.

       -b <DATABASE>
              location    of    database    file.    Default    location    is

       -a <NUMBER>
              arpd not only passively listens ARP on wire, but also send brod-
              cast queries itself. NUMBER is number of such  queries  to  make
              before  destination  is considered as dead. When arpd is started
              as kernel helper (i.e. with app_solicit  enabled  in  sysctl  or
              even with option -k) without this option and still did not learn
              enough information, you can observe 1 second  gaps  in  service.
              Not fatal, but not good.

       -k     Suppress  sending  broadcast  queries  by kernel. It takes sense
              together with option -a.

       -n <TIME>
              Timeout of negative cache. When resolution fails arpd suppresses
              further attempts to resolve for this period. It makes sense only
              together with option -k This timeout  should  not  be  too  much
              longer  than  boot  time of a typical host not supporting gratu-
              itous ARP. Default value is 60 seconds.

       -r <RATE>
              Maximal steady rate of broadcasts sent by arpd  in  packets  per
              second. Default value is 1.

       -B <NUMBER>
              Number  of  broadcasts  sent  by <tt/arpd/ back to back. Default
              value is 3. Together with option <tt/-R/ this option  allows  to
              police  broadcasting  not  to  exceed B+R*T over any interval of
              time T.

       <INTERFACE> is the name of networking interface to watch. If no  inter-
       faces  given,  arpd monitors all the interfaces. In this case arpd does
       not adjust sysctl parameters, it is supposed  user  does  this  himself
       after arpd is started.

       arpd  exits  gracefully  syncing database and restoring adjusted sysctl
       parameters, when receives SIGINT or SIGTERM. SIGHUP syncs  database  to
       disk.  SIGUSR1  sends some statistics to syslog. Effect of another sig-
       nals is undefined, they may corrupt database and leave  sysctl  praame-
       ters in an unpredictable state.

       In  order  for arpd to be able to serve as ARP resolver, 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.

       arpd -b /var/tmp/arpd.db
              Start  arpd to collect gratuitous ARP, but not messing with ker-
              nel functionality.

       killall arpd ; arpd -l -b /var/tmp/arpd.db
              Look at result after some time.

       arpd -b /var/tmp/arpd.db -a 1 eth0 eth1
              Enable kernel helper, leaving leading role to kernel.

       arpd -b /var/tmp/arpd.db -a 3 -k eth0 eth1
              Completely replace kernel  resolution  on  interfaces  eth0  and
              eth1. In this case kernel still does unicast probing to validate
              entries, but all the broadcast activity is suppressed  and  made
              under authority of arpd.

       This is mode which arpd is supposed to work normally. It is not default
       just to prevent occasional enabling of too  aggressive  mode  occasion-

                                 28 June, 2007                         ARPD(8)