Sometimes it can be useful to find out more information about a computer's upstream ISP, as well as its approximate geographic location.
ARIN, The American Registry for Internet Numbers, provides this information on their DNS servers.
In order to get this information from ARIN, you need to query their DNS servers by IP. A lot of times, it's more convenient to look it up by domain name.
The revhost script allows you to do netblock lookups by either IP or domain name automatically. To use it, just type:
[me@myserver]$ revhost oreilly.com
[whois.arin.net]
UUNET Technologies, Inc. UUNET1996B (NET-208-192-0-0-1)
208.192.0.0 - 208.255.255.255
SONIC.NET, INC. UU-208-201-224 (NET-208-201-224-0-1)
208.201.224.0 - 208.201.255.255
# ARIN WHOIS database, last updated 2003-05-07 20:10
# Enter ? for additional hints on searching ARIN's WHOIS database.
Here is the source code listing for revhost. To make it a permanent fixture on your system, make sure it's executable and put it someplace like /usr/local/bin/revhost
------------- BEGIN CODE LISTING -------------
#!/bin/sh
# -----------------------------------------------------------------------------
# revhost
# -----------------------------------------------------------------------------
# performs netblock lookups by hostname or IP by querying the ARIN DNS database
# -----------------------------------------------------------------------------
# requires: whois, host, awk, cut, test/[
# -----------------------------------------------------------------------------
# bail out if we weren't called with an argument
if [ ! $1 ]; then
echo "Usage: revhost [hostname]";
exit;
fi
IP_ADDX="";
# did we get an IP or a hostname?
FIRST_CHAR=`echo $1 | cut -b1`
IS_IP=`expr $FIRST_CHAR + 1 2>/dev/null`
if [ $IS_IP ]; then
# we got an IP
IP_ADDX=$1;
else
# it's a hostname, do a lookup to convert to IP
IP_ADDX=`host $1 | awk '{print $4}' | head -1`;
fi
# query the ARIN DNS server by IP
whois -h whois.arin.net $IP_ADDX;
-------------- END CODE LISTING --------------
See also:
man whois
http://whois.arin.net
