GETETHERS(8L)

NAME
getethers - get ethernet address/hostname information

SYNOPSIS
getethers [ -e ] [ -s ] [ -v ] [ -w ] net [ net... ]

DESCRIPTION

getethers probes the specified network(s), whose addresses are given in Internet ``dot'' notation, and produces a list of host name and ethernet address pairs for each host on the network that responds to ICMP ECHO_REQUEST packets. The program assumes a subnet mask of 255.255.255.0 (0xffffff00), and does not probe host number 0 or host number 255, which are used as the broadcast address.

If the -v option is specified, a list is produced on the standard output that contains the host name, internet address, ethernet address, and vendor name of the ethernet board for each host that responded to ICMP ECHO_REQUEST packets.

If the -w option is specified, along with either the -e or -s options, a file will be written for each network that can be used with the Excelan Lanalyzer (-e) or Network General Sniffer (-s) products as a name-to-address translation file. The name of the file will be XXXnet.nam, where XXX is the last byte of the network address.

getethers works by first probing the system's ethernet interfaces, looking for the interface that is connected to the specified network. If the system is not connected to that network, getethers prints an error message and goes on to the next network. After discovering the proper interface, getethers sends up to three ICMP ECHO_REQUEST packets to each host number on that network from 1 to 254. If the host responds, getethers then searches the local host's arp table for the remote host's ethernet address. If the remote host does not respond to the ECHO_REQUEST packets within three seconds, it is assumed to be down or non-existent, and is skipped.

SEE ALSO
arp(4P), arp(8C), etherfind(8C), ethers(3N), icmp(4P), inet(3N), nit(4P), ping(8C), rarpd(8C)

BUGS

The assumption of a 255.255.255.0 subnet mask, and the assumption of all-zero or all-ones as a broadcast address, are probably not good ideas and should be determined at run-time, but it works in our environment.

The Lanalyzer file, due to its fixed size, cannot handle more than 100 entries. If a network has more than 100 hosts connected (and up), the file will not be usable (or at least the stuff after 100 entries won't be).

AUTHOR
David A. Curry, Purdue University Engineering Computer Network