Finding available IP addresses on network?

How can i find out what IP addresses are available on a windows network?

Probably something simple but i cant think how to do this...

Help appreciated.

r3b007

As long as all your hosts are set up to respond to pings, you could just write a script to ping every IP. The ones that don't respond are available.

If you run a DHCP server, then it will know which ones are available.

I'm guessing however, that you have static IPs. If this is the case, you can ping them all, but beware the machines which aren't turned on :)

The most robust way of doing it is to go around manually cataloguing them. However it will be a pain in the arse (esp. the laptop that the company director has taken on holiday with him)

Yeah, all the machines have static IP's so i guess i was wrong about it being something simple :rolleyes:

Thanks for the reply

the easiest way to scan for (online) ip adresses:

say you want to scan all ip's starting with 192.168

nmap -sP 192.168.*.*

but then you'll have to know that they are all on !!

Its a windows server so nmap is no good!

If you are running a WINS/DDNS service on the Windows network you can get the IP information from this database.
Ping sweeps will also do the trick, but is very noizy on large networks and like said before will only catch active NICs. Very easy to assign duplicate IPs that way.

Apologise if me being daft first post and all..but just try a scanning tool like this one www.lookatlan.com slong as you know your starting ip just let her go and shell come back with a list of empty/unused

Thanks for all the useful replies guys.
Ill try out some of the suggestions.

Cheers

Not daft Shaggy100..

Languard is another tool .. and basicly as the_JinX's instructed.. set it to scann ie 192.168.0.0 - 192.168.0.255
b4 you start:..just be sure you won't get shot by the admin for doing a scann
that is for any prog or script you could use to "scann" for available IP's..

BTW.. I am too lazy to check.. But isn't there a Win version of nmap?

Cheers

There is a Windows version of nmap, it will work fine. You can ping scan your network (which just pings the boxes), and easily tell which ones are up.

I'd still recommend a physical audit (provided there aren't too many boxes), as it will catch anything not turned on.

You can't rely on WINS or DDNS to give you the IP of every device on the network, because it's not guaranteed that all hosts will be in it. For instance, some Windows boxes might not be part of the domain, or other devices (usually switches, routers and printers) will be using IP addresses.

As far as being shot by the admin is concerned, I was assuming that you *were* the admin. I was certainly in a similar situation a few years ago, and had to catalogue all the static IPs and hunt out a few rogue devices.

I am not the admin, i am working with him trying to get a device setup on his network but he didnt know what IPs were available to use.
The network isnt too big, so the suggestions that have been made should do the trick.

ps Ive heard that the windows version of nmap aint that great...

ya, I've tried using NmapWin and I personally think it sucks....especially compared to other scanners made just for windows. If you're using something like Linux though, Nmap rules.

NmapWin isn't that bad.

It does actually work. Sometimes it seems to pause for a long time for no reason, but I think that's Windows' resolver library, not really nmap's fault.

It will be completely adequate for ping-scanning your network to determine which IPs are being used.

Just a side thought if you are pinging all the machines... I don't know if I missed someone saying this or not but you have to make sure ALL the machiens are on for you to get an accurate picture of what IPs are in use... seeing as they are setup statically. Because if the machine is off it won't respond, but it will still have an IP setup to it.

Just a thought...
~AciD

r3b00+:
- Scans like Nmap is a bit of a brut force solution.
- It depends of the network size and management but maybe u could get the info by getting ARP tables of few key devices (routers, switch, ...).
ARP cache is oftently timout in 20 mns, but SMTP activities should maintain up-to-date all arp tables.
You copy the data in an excell sheet one day and again 2 hours and it should give you quite an accurate vission of IP being is use.

Anyway every single networking device and even PCs can detect IP@ duplication. They should alert u quiet quickly if an error occured.