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GUESSNET-SCAN(8) System Manager's Manual GUESSNET-SCAN(8)


guessnet-scan - guess network configuration data by looking at network traffic


guessnet-scan [options] [ethernet_interface]


Guessnet-scan tries to deduce network configuration data by watching network traffic at a given Ethernet interface.

After scanning network traffic for some time, guessnet-scan prints a configuration string suitable for inclusion in /etc/network/interfaces.

Note that guessnet-scan uses heuristics and wild guesses and that the resulting data is not guaranteed to be accurate. The program is intended to be used as a first try at getting network configuration data without bothering anyone.


Options follow the usual GNU conventions,

Print debugging messages.
Show a brief summary of commandline options.
Time in seconds to wait for the interface to initialize when it is not found already up at program startup. Default: 3 seconds.
Time in seconds to watch for network traffic. Default: 5 seconds.
Operate verbosely.
Show the version number of the program.


To correctly identify all data of the local network, guessnet-scan needs to see traffic related to a host in the local network and to the local gateway, if any.

To be able to identify the network gateway, guessnet-scan also needs to see some traffic directed to the external network: you can help the detection by generating some outbound IP traffic during the scan, for example by browsing a web page (without proxy) or using telnet to open a connection to some remote host.

Note that if you are connected to a switch, guessnet-scan won't probably be able to work, since the switch will isolate it from the network traffic that the other machines are generating.


guessnet(8), interfaces(5).


Guessnet-scan was written by Enrico Zini <>.

10 October 2004