NOTE: This is not a native "dos" command. You can, however, run it from a command line interface or "dos" as you call it.
get nmap from www.insecure.org

If all machines respond to icmp echo/echo-reply, then you can do a ping scan.
<aka> ping sweep

using nmap...

nmap -sP 192.168.1.0/24

That will ping each ip and report back if a host is alive or dead...

NOTE: You can also combine this with -vv (verbose) to get more info.

This will only work IF the hosts in question respond to ICMP echo/echo-reply.

If not, then you can try other scans... without the ping option.

nmap -sV -O -P0 -vv 192.168.1.0/24

That will probe the computers and try to determine which services and operating system it is running. The -P0 tells it not to ping... or ignore host discovery.

nmap -sS -vv -P0 192.168.1.0/24

that will syn scan with verbose info without host discovery.

Check out the nmap man file or help file for more combinations.

You will need WINPCAP if you're using the win32 nmap binary.