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 [ -dNp ] [ -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 -p flag disables promiscous mode.
23 The -f flag is used to set the ethernet/ip address database filename.
25 The default is arp.dat.
26 The -i flag is used to override the default interface.
28 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.
33 The -N flag disables reporting any bogons.
35 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.
39 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.
43 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.)
49 If the -s flag is used, arpwatch sends e-mail messages with username as
51 the return address, rather than the default (root).
52 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.
56
58 Here's a quick list of the report messages generated by arpwatch(1)
59 (and arpsnmp(1)):
60 new activity
62 This ethernet/ip address pair has been used for the first time
63 six months or more.
64 new station
66 The ethernet address has not been seen before.
67 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.)
74 changed ethernet address
76 The host switched to a new ethernet address.
77
79 Here are some of the syslog messages; note that messages that are
80 reported are also sysloged.
81 ethernet broadcast
83 The mac ethernet address of the host is a broadcast address.
84 ip broadcast
86 The ip address of the host is a broadcast address.
87 bogon The source ip address is not local to the local subnet.
89 ethernet broadcast
91 The source mac or arp ethernet address was all ones or all
92 zeros.
93 ethernet mismatch
95 The source mac ethernet address didn't match the address inside
96 the arp packet.
97 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.)
102 suppressed DECnet flip flop
104 A "flip flop" report was suppressed because one of the two
105 addresses was a DECnet address.
106
108 /var/lib/arpwatch - default directory
109 arp.dat - ethernet/ip address database
110 ethercodes.dat - vendor ethernet block list
111
113 arpsnmp(8), arp(8), bpf(4), tcpdump(1), pcapture(1), pcap(3)
114
116 Craig Leres of the Lawrence Berkeley National Laboratory Network Re‐
117 search Group, University of California, Berkeley, CA.
118 The current version is available via anonymous ftp:
120 ftp://ftp.ee.lbl.gov/arpwatch.tar.gz
122
124 Please send bug reports to arpwatch@ee.lbl.gov.
125 Attempts are made to suppress DECnet flip flops but they aren't always
127 successful.
128 Most error messages are posted using syslog.
1304th Berkeley Distribution 8 October 2000 ARPWATCH(8)