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RedHat 9 (Linux i386) - man page for arpwatch (redhat section 8)

ARPWATCH(8)			     System Manager's Manual			      ARPWATCH(8)

       arpwatch - keep track of ethernet/ip address pairings

       arpwatch [ -dN ] [ -f datafile ] [ -i interface ]
		[ -n net[/width ]] [ -r file ] [ -u username ] [ -e username ] [ -s username ]

       Arpwatch  keeps	track  for  ethernet/ip address pairings. It syslogs activity and reports
       certain changes via email.  Arpwatch uses pcap(3) to listen for arp  packets  on  a  local
       ethernet interface.

       The  -d	flag is used enable debugging. This also inhibits forking into the background and
       emailing the reports. Instead, they are sent to stderr.

       The -f flag is used to set the ethernet/ip address  database  filename.	 The  default  is

       The -i flag is used to override the default interface.

       The -n flag specifies additional local networks. This can be useful to avoid "bogon" warn-
       ings when there is more than one network running on the same wire. If the  optional  width
       is not specified, the default netmask for the network's class is used.

       The -N flag disables reporting any bogons.

       The  -r	flag is used to specify a savefile (perhaps created by tcpdump(1) or pcapture(1))
       to read from instead of reading from the network. In this case, arpwatch does not fork.

       If -u flag is used, arpwatch drops root privileges and changes user  ID	to  username  and
       group  ID to that of the primary group of username.  This is recommended for security rea-

       If the -e flag is used, arpwatch sends e-mail messages to username rather than the default
       (root).	 If  a	single `-' character is given for the username, sending of e-mail is sup-
       pressed, but logging via syslog is still done as usual.	(This can be useful  during  ini-
       tial runs, to collect data without being flooded with messages about new stations.)

       If  the	-s  flag  is  used,  arpwatch  sends  e-mail messages with username as the return
       address, rather than the default (root).

       Note that an empty arp.dat file must be created before the first time  you  run	arpwatch.
       Also, the default directory (where arp.dat is stored) must be owned by username if -u flag
       is used.

       Here's a quick list of the report messages generated by arpwatch(1) (and arpsnmp(1)):

       new activity
	      This ethernet/ip address pair has been used for the first time six months or more.

       new station
	      The ethernet address has not been seen before.

       flip flop
	      The ethernet address has changed from the most recently seen address to the  second
	      most recently seen address.  (If either the old or new ethernet address is a DECnet
	      address and it is less than 24 hours, the email  version	of  the  report  is  sup-

       changed ethernet address
	      The host switched to a new ethernet address.

       Here  are  some of the syslog messages; note that messages that are reported are also sys-

       ethernet broadcast
	      The mac ethernet address of the host is a broadcast address.

       ip broadcast
	      The ip address of the host is a broadcast address.

       bogon  The source ip address is not local to the local subnet.

       ethernet broadcast
	      The source mac or arp ethernet address was all ones or all zeros.

       ethernet mismatch
	      The source mac ethernet address didn't match the address inside the arp packet.

       reused old ethernet address
	      The ethernet address has changed from the most recently seen address to  the  third
	      (or greater) least recently seen address.  (This is similar to a flip flop.)

       suppressed DECnet flip flop
	      A  "flip	flop" report was suppressed because one of the two addresses was a DECnet

       /usr/operator/arpwatch - default directory
       arp.dat - ethernet/ip address database
       ethercodes.dat - vendor ethernet block list

       arpsnmp(8), arp(8), bpf(4), tcpdump(1), pcapture(1), pcap(3)

       Craig Leres of the Lawrence Berkeley National Laboratory Network Research Group, Universi-
       ty of California, Berkeley, CA.

       The current version is available via anonymous ftp:


       Please send bug reports to arpwatch@ee.lbl.gov.

       Attempts are made to suppress DECnet flip flops but they aren't always successful.

       Most error messages are posted using syslog.

4th Berkeley Distribution		  8 October 2000			      ARPWATCH(8)

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