1ARPWATCH(8) System Manager's Manual ARPWATCH(8)
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6 arpwatch - keep track of ethernet/ip address pairings
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9 arpwatch [ -dN ] [ -f datafile ] [ -i interface ]
10 [ -n net[/width ]] [ -r file ] [ -u username ] [ -e username ]
11 [ -s username ]
12
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.
17 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.
21 The -f flag is used to set the ethernet/ip address database filename.
23 The default is arp.dat.
24 The -i flag is used to override the default interface.
26 The -n flag specifies additional local networks. This can be useful to
28 avoid "bogon" warnings when there is more than one network running on
29 the same wire. If the optional width is not specified, the default net‐
30 mask for the network's class is used.
31 The -N flag disables reporting any bogons.
33 The -r flag is used to specify a savefile (perhaps created by tcp‐
35 dump(1) or pcapture(1)) to read from instead of reading from the net‐
36 work. In this case, arpwatch does not fork.
37 If -u flag is used, arpwatch drops root privileges and changes user ID
39 to username and group ID to that of the primary group of username.
40 This is recommended for security reasons.
41 If the -e flag is used, arpwatch sends e-mail messages to username
43 rather than the default (root). If a single `-' character is given for
44 the username, sending of e-mail is suppressed, but logging via syslog
45 is still done as usual. (This can be useful during initial runs, to
46 collect data without being flooded with messages about new stations.)
47 If the -s flag is used, arpwatch sends e-mail messages with username as
49 the return address, rather than the default (root).
50 Note that an empty arp.dat file must be created before the first time
52 you run arpwatch. Also, the default directory (where arp.dat is
53 stored) must be owned by username if -u flag is used.
54
56 Here's a quick list of the report messages generated by arpwatch(1)
57 (and arpsnmp(1)):
58 new activity
60 This ethernet/ip address pair has been used for the first time
61 six months or more.
62 new station
64 The ethernet address has not been seen before.
65 flip flop
67 The ethernet address has changed from the most recently seen
68 address to the second most recently seen address. (If either
69 the old or new ethernet address is a DECnet address and it is
70 less than 24 hours, the email version of the report is sup‐
71 pressed.)
72 changed ethernet address
74 The host switched to a new ethernet address.
75
77 Here are some of the syslog messages; note that messages that are
78 reported are also sysloged.
79 ethernet broadcast
81 The mac ethernet address of the host is a broadcast address.
82 ip broadcast
84 The ip address of the host is a broadcast address.
85 bogon The source ip address is not local to the local subnet.
87 ethernet broadcast
89 The source mac or arp ethernet address was all ones or all
90 zeros.
91 ethernet mismatch
93 The source mac ethernet address didn't match the address inside
94 the arp packet.
95 reused old ethernet address
97 The ethernet address has changed from the most recently seen
98 address to the third (or greater) least recently seen address.
99 (This is similar to a flip flop.)
100 suppressed DECnet flip flop
102 A "flip flop" report was suppressed because one of the two
103 addresses was a DECnet address.
104
106 /var/lib/arpwatch - default directory
107 arp.dat - ethernet/ip address database
108 ethercodes.dat - vendor ethernet block list
109
111 arpsnmp(8), arp(8), bpf(4), tcpdump(1), pcapture(1), pcap(3)
112
114 Craig Leres of the Lawrence Berkeley National Laboratory Network Re‐
115 search Group, University of California, Berkeley, CA.
116 The current version is available via anonymous ftp:
118 ftp://ftp.ee.lbl.gov/arpwatch.tar.gz
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122 Please send bug reports to arpwatch@ee.lbl.gov.
123 Attempts are made to suppress DECnet flip flops but they aren't always
125 successful.
126 Most error messages are posted using syslog.
1284th Berkeley Distribution 8 October 2000 ARPWATCH(8)