Linux – Scan for connected, powered on computers on a network

icmplinuxnetworkingnmapping

I want to scan for powered on computers on my LAN and gather logs about that. I tried nmap but it didn't work very well (a lot of switched on computers are not getting detected).

nmap -sP 192.168.2.0/24
Nmap done: 256 IP addresses (10 hosts up) scanned in 6.07 seconds

I also thought about looking at network TCP packets for IPs, but I don't know of any tool ready to do that.

On this network, all computers have static IPs associated, so a IP identifies a computer. The PCs have different operating systems (Windows 7, Ubuntu 10.04, Ubuntu 12.04 and more).

What's my best chance?

Best Answer

Have you tried other scan options from nmap? The ping option may not always work, but other scan options may be more reliable? Try,

nmap -PS 192.168.2.0/24 (TCP SYN ping)

nmap -PR 192.168.2.0/24 (ARP scan)

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Ssh – How to scan local network for SSH-able computers

Use "nmap" - this will tell you which hosts are up on a network, and indeed which have port 22 open. You could combine it with a few other tools (like grep) to produce more targeted output if need be.

Note: do this only on YOUR network. Running up nmap or its equivalents on someone else's network is considered bad form.

sudo nmap -p 22 192.168.0.0/24

Nmap does not find alive hosts with ping scan

Just tried this with my OpenBSD 5.1. Yes, you have FreeBSD 7.4, but we are talking quite a similar beast.

As a regular user, nmap -sn my.host returns Host seems down for me, too, even though my test machine surely responds to ping as a regular user.

As root, however, nmap -sn my.host returns Host is up as it should.

Looking at your prompt, you are likely also trying to nmap as a non-root user. Try if nmap works as root.

EDIT: Just fired up my FreeBSD 9.0, there nmap ping scan works fine as non-root.

Best Answer

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Ssh – How to scan local network for SSH-able computers

Nmap does not find alive hosts with ping scan

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