1ARPWATCH(8)                 System Manager's Manual                ARPWATCH(8)
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NAME

6       arpwatch - keep track of ethernet/ip address pairings
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SYNOPSIS

9       arpwatch [ -dNp ] [ -f datafile ] [ -i interface ]
10                [ -n net[/width ]] [ -r file ] [ -u username ] [ -e username ]
11       [ -s username ]
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DESCRIPTION

14       Arpwatch keeps track  for  ethernet/ip  address  pairings.  It  syslogs
15       activity  and reports certain changes via email.  Arpwatch uses pcap(3)
16       to listen for arp packets on a local ethernet interface.
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18       The -d flag is used enable debugging. This also inhibits  forking  into
19       the  background  and  emailing  the  reports. Instead, they are sent to
20       stderr.
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22       The -p flag disables promiscous mode.
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24       The -f flag is used to set the ethernet/ip address  database  filename.
25       The default is arp.dat.
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27       The -i flag is used to override the default interface.
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29       The  -n flag specifies additional local networks. This can be useful to
30       avoid "bogon" warnings when there is more than one network  running  on
31       the same wire. If the optional width is not specified, the default net‐
32       mask for the network's class is used.
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34       The -N flag disables reporting any bogons.
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36       The -r flag is used to specify a  savefile  (perhaps  created  by  tcp‐
37       dump(1)  or  pcapture(1)) to read from instead of reading from the net‐
38       work. In this case, arpwatch does not fork.
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40       If -u flag is used, arpwatch drops root privileges and changes user  ID
41       to  username  and  group  ID  to that of the primary group of username.
42       This is recommended for security reasons.
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44       If the -e flag is used, arpwatch  sends  e-mail  messages  to  username
45       rather than the default (root).  If a single `-' character is given for
46       the username, sending of e-mail is suppressed, but logging  via  syslog
47       is  still  done  as usual.  (This can be useful during initial runs, to
48       collect data without being flooded with messages about new stations.)
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50       If the -s flag is used, arpwatch sends e-mail messages with username as
51       the return address, rather than the default (root).
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53       Note  that  an empty arp.dat file must be created before the first time
54       you run arpwatch.   Also,  the  default  directory  (where  arp.dat  is
55       stored) must be owned by username if -u flag is used.
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REPORT MESSAGES

58       Here's  a  quick  list  of the report messages generated by arpwatch(1)
59       (and arpsnmp(1)):
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61       new activity
62              This ethernet/ip address pair has been used for the  first  time
63              six months or more.
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65       new station
66              The ethernet address has not been seen before.
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68       flip flop
69              The  ethernet  address  has  changed from the most recently seen
70              address to the second most recently seen  address.   (If  either
71              the  old  or  new ethernet address is a DECnet address and it is
72              less than 24 hours, the email version  of  the  report  is  sup‐
73              pressed.)
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75       changed ethernet address
76              The host switched to a new ethernet address.
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SYSLOG MESSAGES

79       Here  are  some  of  the  syslog  messages; note that messages that are
80       reported are also sysloged.
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82       ethernet broadcast
83              The mac ethernet address of the host is a broadcast address.
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85       ip broadcast
86              The ip address of the host is a broadcast address.
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88       bogon  The source ip address is not local to the local subnet.
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90       ethernet broadcast
91              The source mac or arp ethernet  address  was  all  ones  or  all
92              zeros.
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94       ethernet mismatch
95              The  source mac ethernet address didn't match the address inside
96              the arp packet.
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98       reused old ethernet address
99              The ethernet address has changed from  the  most  recently  seen
100              address  to  the third (or greater) least recently seen address.
101              (This is similar to a flip flop.)
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103       suppressed DECnet flip flop
104              A "flip flop" report was  suppressed  because  one  of  the  two
105              addresses was a DECnet address.
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FILES

108       /var/lib/arpwatch - default directory
109       arp.dat - ethernet/ip address database
110       ethercodes.dat - vendor ethernet block list
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SEE ALSO

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

116       Craig  Leres  of  the Lawrence Berkeley National Laboratory Network Re‐
117       search Group, University of California, Berkeley, CA.
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119       The current version is available via anonymous ftp:
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121              ftp://ftp.ee.lbl.gov/arpwatch.tar.gz
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BUGS

124       Please send bug reports to arpwatch@ee.lbl.gov.
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126       Attempts are made to suppress DECnet flip flops but they aren't  always
127       successful.
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129       Most error messages are posted using syslog.
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1334th Berkeley Distribution       8 October 2000                     ARPWATCH(8)
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