Finding the ip of a neighbor linux box

jomy · 01-08-2005, 08:27 AM

Hi,

Is there any way to find out the ip address of a neighbour linux box without doing anything on the neighbour box.I don't want to change the ip-address . just to know whether it is possible to find the ip from another system.

Jomy

jeickal · 01-08-2005, 11:56 AM

Assuming you are on the same LAN, there are several ways of doing this. Here is one:

Ping your broadcast address.
Check out the new entry in your arp table.

To find out your broadcast address:
Open a shell, and su to root. Type:

Code:

ifconfig eth0

replace "eth0" by whatever suit your system or just don't put it and it will display all your NIC's info
Then look for sth like this ==> Bcast:192.168.1.255 <== this is my broadcast address.

Now ping it:

Code:

ping -b 192.168.1.255

Let it go for a couple of sec and then hit ctrl+c
Now type:

Code:

arp -a

That'll show you the hostname (1st column) the IP address (2nd one) the Mac address (3rd one) of all the machine in your LAN that answered the broadcast.

Note that if one box as a firewall loaded, this wont work (the firewall will block the ping)

Hangdog42 · 01-08-2005, 02:37 PM

The best way to find out is to ask the neighbor. If they won't tell you, you have no business trying to do anything else to figure it out.

Be aware the LQ does not allow threads about cracking or attacking other systems

jeickal · 01-08-2005, 03:21 PM

Quote:

The best way to find out is to ask the neighbor. If they won't tell you, you have no business trying to do anything else to figure it out

I partially disagree with this. It depens on the circumptances. I'm a network admin, and knowing how to "trace" an IP has been extremely usefull to me many times.
I said partially because you're obviously right about the fact that helping others to do bad things has no place in this forum. But any help you give can be use to do bad things so where is the limit? If one guy asks for help to install a sniffer on his machine, should you not answer because he could use it to steal passwords? I'm using sniffers to do my job, not to steal password. You see my point?

I did think about it before answering this post. And I concluded that this does not cross the line (yet). I'll keep helping as long as I believe we stay on the right side. If you think I'm wrong, then ask a moderator to decide.

Hangdog42 · 01-08-2005, 04:02 PM

Quote:

Originally posted by jeickal
I partially disagree with this. It depens on the circumptances.

Given the conditions of your answer, yes, this thread is almost certainly on acceptable ground. However, the original question was vague enough that my interpretation was that the poster was referring to a computer that wasn't part of the LAN, and this thread had the potential to head in the wrong direction. If I'm wrong, both you and Jomy have my apologies.