Personal computing discussed

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Crayon Shin Chan
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How to list all computers on a subnet?

Tue Sep 07, 2010 5:41 am

So I would like to find out what computers in a particular subnet are up. Usually I would just use arp -a for that, except for the fact that sometimes, I have to ping an IP before its MAC address gets added to the list. And take a look at this:
Interface: 192.168.1.2 --- 0x2
  Internet Address      Physical Address      Type
  192.168.1.1           booooooooooooo     dynamic
  192.168.1.3           hahahhahahahahah     dynamic
  192.168.1.4           hahahahahahaha     dynamic
  192.168.1.13          00-00-00-00-00-00     invalid
  192.168.1.14          00-00-00-00-00-00     invalid
  192.168.1.15          00-00-00-00-00-00     invalid
  192.168.1.16          00-00-00-00-00-00     invalid
  192.168.1.86          00-00-00-00-00-00     invalid
  192.168.1.87          00-00-00-00-00-00     invalid
  192.168.1.88          00-00-00-00-00-00     invalid

What's with all those invalids?

I've heard of broadcast pings, but it seems that every OS nowadays doesn't respond to broadcast pings because of some old attack called the Smurf attack. Bottom line, ping -b 192.168.1.255 or on Windows, ping 192.168.1.255 doesn't work. Oh, I think I got OS X to respond to a broadcast ping. But it wasn't the only computer on the subnet.

Then there's this utility called Net World Scanner for Windows. Turns out it only works with Windows computers with a NetBIOS name - my Linux virtual machine that's not running Samba never showed up.

Any ideas?
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redeye
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Re: How to list all computers on a subnet?

Tue Sep 07, 2010 6:49 am

Crayon Shin Chan wrote:
Then there's this utility called Net World Scanner for Windows. Turns out it only works with Windows computers with a NetBIOS name - my Linux virtual machine that's not running Samba never showed up.

Any ideas?


Sounds to me like your LinuxVM doesn't have a IP addr. Can you check and see what IP address it's using?
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Crayon Shin Chan
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Re: How to list all computers on a subnet?

Tue Sep 07, 2010 7:15 am

192.168.1.4 via DHCP.
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redeye
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Re: How to list all computers on a subnet?

Tue Sep 07, 2010 7:18 am

What's the IP address of the windows box it's running on?

Edit: added clarification on the question.
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Crayon Shin Chan
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Re: How to list all computers on a subnet?

Tue Sep 07, 2010 7:20 am

192.168.1.2 windows desktop
192.168.1.3 windows laptop
all assigned by DHCP

EDIT: no computer is missing in the above arp -a output. My point is there are entries with invalid MAC addresses... and it's not guaranteed that the computers on the arp -a output are the only ones on the subnet.
Mothership: Thuban 1055T@3.7GHz, 12GB DDR3, M5A99X EVO, GTX470+Icy Vision Rev.2@840/3800, Vertex 2E 60GB
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redeye
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Re: How to list all computers on a subnet?

Tue Sep 07, 2010 7:32 am

I'm more interested in the Net World Scanner output. Arp -a only lists the mac addresses that machine knows and they time out after not hearing for them from a time. A broadcast ping used to be able to take care of this problem as everything would generally respond, but now many devices do not reply to a broadcast ping. I just tried the Net World Scanner and it definitely sucks. Try netping, that was able to find everything on my network.
"I am too old to die young, and too young to grow up," - Marty Feldman
 
Scrotos
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Re: How to list all computers on a subnet?

Tue Sep 07, 2010 7:39 am

http://www.mikrotik.com/thedude.php

There's a neat Windows thing that lets you scan entire subnets. And it's free!
 
notfred
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Re: How to list all computers on a subnet?

Tue Sep 07, 2010 9:38 am

Get a managed switch and dump the MAC-to-port mapping table.
 
Crayon Shin Chan
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Re: How to list all computers on a subnet?

Tue Sep 07, 2010 9:57 am

Net World Scanner only detects the two Windows computers.

I've downloaded the Dude, haven't installed it yet. It looks way too complex for what I want. Mapping functions? Also, managed switches could buy me a whole new computer.
Mothership: Thuban 1055T@3.7GHz, 12GB DDR3, M5A99X EVO, GTX470+Icy Vision Rev.2@840/3800, Vertex 2E 60GB
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kyboshed
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Re: How to list all computers on a subnet?

Tue Sep 07, 2010 10:28 am

I use Netscan (http://www.softperfect.com/products/networkscanner/). It's free, simple and lists every machine (real & virtual) on my network in a minute or so.
 
unkoil
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Re: How to list all computers on a subnet?

Tue Sep 07, 2010 10:35 am

 
flip-mode
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Re: How to list all computers on a subnet?

Tue Sep 07, 2010 11:29 am

nmap in linux
 
arsenhazzard
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Re: How to list all computers on a subnet?

Thu Sep 09, 2010 12:32 am

flip-mode wrote:
nmap in linux


nmap works fine on Windows as well...

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