arpwatch

Langue: en

Version: 8 October 2000 (openSuse - 09/10/07)

Section: 8 (Commandes administrateur)

NAME

arpwatch - keep track of ethernet/ip address pairings

SYNOPSIS

arpwatch [ -dN ] [ -f datafile ] [ -i interface ]

         [ -n net[/width ]] [ -r file ]

DESCRIPTION

Arpwatch keeps track for MAC/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/tokenring/fddi 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 MAC/IP address database filename. The default is arp.dat.

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

The -n flag specifies additional local networks. This can be useful to avoid "bogon" warnings 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.

Note that an empty arp.dat file must be created before the first time you run arpwatch.

REPORT MESSAGES

Here's a quick list of the report messages generated by arpwatch(1) (and arpsnmp(1)):
new activity
This MAC/IP address pair has been used for the first time six months or more.
new station
The MAC address has not been seen before.
flip flop
The MAC address has changed from the most recently seen address to the second most recently seen address. (If either the old or new MAC address is a DECnet address and it is less than 24 hours, the email version of the report is suppressed.)
changed MAC address
The host switched to a new MAC address.

SYSLOG MESSAGES

Here are some of the syslog messages; note that messages that are reported are also sysloged.
MAC broadcast
The MAC 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.
MAC broadcast
The source MAC address was all ones or all zeros.
MAC mismatch
The source MAC address didn't match the address inside the arp packet.
reused old MAC address
The MAC 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 address.

FILES


/usr/operator/arpwatch - default directory

arp.dat - MAC/IP address database

ethercodes.dat - vendor ethernet block list

SEE ALSO

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

AUTHORS

Craig Leres of the Lawrence Berkeley National Laboratory Network Research Group, University of California, Berkeley, CA.

The current version is available via anonymous ftp:

ftp://ftp.ee.lbl.gov/arpwatch.tar.gz

BUGS

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.