For analytics purposes, I'm looking at large sets of IP addresses in server log files. I'm trying to perform reverse-DNS lookups to understand where traffic is coming from - e.g. what percentage of IPs resolve to corporations, schools, government, international etc.

Despite a bunch of optimizations, individually reverse-DNS'ing every IP address still appears to be fairly expensive though. So -

is there any way to obtain an entire range of IPs from a reverse-DNS?

If yes, this could greatly reduce the number of actual reverse-DNS lookups.

Example (numbers slightly obfuscated): 


Log file contains a request from an IP 128.151.162.17
Reverse DNS resolves to 11.142.152.128.in-addr.arpa 21599 IN PTR alamo.ceas.rochester.edu
(So this is a visitor from Rochester University, rochester.edu)
Now, would it be safe to assume that all at least all IPs from 128.151.162.* will also resolve to rochester.edu?
What about 128.151.*.*? Is there a way to get the exact IP range?



Question: Using Pi to stream all audio output from my pc to my stereo
Answer: The "LineInCode"-Solution described here works - but the sound is terrible over wifi. The VLC-Solution provided above works too - but it need a lot of clicking. I combined both in a batch-file which would start VLC as a streamer on my PC and mpg123 as a "listner" on the PI. It works like a charm for me. You need to have Plik in the same folder (we use it as ssh-client). I use this script from today on to listen to mp3s on my laptop, while the soundoutput is the pi:

            REM This is fischteich's start_sound.bat v 0.3
            @echo off

            set vlc="C:\Program Files (x86)\VideoLAN\VLC\vlc.exe"
            set ssh-login=YOURLOGIN
            set ssh-pw=YOURPW
            set this-machine-ip=192.168.XXX.XXX
            set pi-ip=192.168.XXX.XXX
            set use-port=5001

            set start-string= --sout-keep --sout=#transcode{vcodec=none,acodec=mp3,ab=192,channels=2,samplerate=44100}:http{mux=mp3,dst=:%use-port%/}

            REM Start VLC ready for files to play
            @start "vlc" %vlc% %start-string%
            REM Start playback via mpg123 on the Pi!
            plink %pi-ip% -l %ssh-login% -pw %ssh-pw% "mpg123 http://%this-machine-ip%:%use-port%"