tutorial - First step in hacking - know your neighboring machines

The simplest way I can do is use ping, I can send a broadcast packet to everyone in a subnet, so that they can response back. Let say I am in subnet of 192.168.0.x and the broadcast IP is 192.168.0.255, I can do this:

ping -b 192.168.0.255

How I know the broadcast IP is 192.168.0.255? I can check with ifconfig.

ifconfig eth0 | grep Bcast

Some routers are configured to filter broadcast and multicast packets to prevent broadcast storm, if so, broadcast is useless.

So what are the alternatives way?

I can ping the IP one by one with a line of bash script.

for ((i=1;i<255;i++));>

The result will look like this:

--- 192.168.0.1 ping statistics ---
--- 192.168.0.2 ping statistics ---
--- 192.168.0.3 ping statistics ---
--- 192.168.0.4 ping statistics ---
64 bytes from 192.168.0.5: icmp_seq=1 ttl=249 time=11.0 ms
--- 192.168.0.5 ping statistics ---
64 bytes from 192.168.0.6: icmp_seq=1 ttl=248 time=12.3 ms
--- 192.168.0.6 ping statistics ---
--- 192.168.0.7 ping statistics ---
--- 192.168.0.8 ping statistics ---
--- 192.168.0.9 ping statistics ---
--- 192.168.0.10 ping statistics ---
--- 192.168.0.11 ping statistics ---

Let me explain the ping options I use, -c (count) indicates how many attempt of ping for a single IP, -W specified the timeout in second, ping will waits until timeout to declare the attempt is fail.

From the sample results, I discovered 192.168.0.5 and 192.168.0.6.

Due to the limitation of ping, I can’t specified the timeout less than 1 seconds, to scan a class C LAN, it may takes up 255 seconds, which is extremely slow.

Free, facebook, tips, Links, blogging, Downloads, Google, facebookTips, money, news, apps, Social, Media, Website, Tricks, games, Android, software, PIctures, Internet, Security, Web, codes, Review, bloggers, SAMSUNG, Worldwide, Contest, Exitic, Phones, facebookTricks, hacking, London, Olympics, SEO, Youtube, iOS, Adsense, gadgets, iPHONE, widgets, Doodle, twitter, video, Deals, technology, Aircel, Airtel, iPAD, Angry, Birds, BSNL, TechLife, GMAIL, Idea, Microsoft, SmartPhones, Stress, Buster, Windows, Yahoo, Infolinks, Nokia, Scam, Uninor, browsers, Amazon, Euro, CUP, Chat, IDM, JOBS, Modem, Music, Reliance, Results, SSC, Tata, Docomo, bing, freebie, mobile, placements, AIEEE, AlertPay, Chrome, College, Competetive, Exam, Dehradun, Extension, FireFox, GPRS, HTC, IMPACT, Info, MTS, Mark, Zukerberg, Paypal, Promotional, Post, Torrent, UTU, Unlocking, VodaFone, Wall, Paper, apple, books, engineering, iCAR, iTunes, pinterest, rovio, AVG, Admit, Card, Adobe, Affiliate, Marketing, Akhilesh, Amul, Girl, BlackBerry, ChromeBook, Clixsense, Coupon, Digitallife, Discovery, Emoticons, Festival, GATE, GIMP, Income, Tax, International, JSS, JailBreaking, Kindle, Linux, Local, MAX, PAYNE, Mac, Mango, Memory, Speed, Nexus, Online, Shopping, Raakhi, Report, Rising, Stars, Sample, Science, Sony, Syllabus, TabletBooK, Teamviewer, Templates, Dark, Knight, Rises, USA, UPMT, Virgin, Xperia, ZTE, challan, counselling, course, btech, funny, iMOVE, registration

source:http://linuxpoison.blogspot.com/2008/02/13578175809338.html