Mapping Class A network ( any easy trick?)

[John Thomas <mjohn2000_99 () yahoo com>]

I am about to do a penetration testing on a “Class A
network” and wondering how I can map the network
without pinging 17 million IPs.(nmap -Sp 10.0.0.0/8) 

I did some research and the best information I got is
from one of the earlier post on this
list(http://seclists.org/lists/pen-test/2004/Jul/0067.html)
. It was to use broadcast IPs for pings. But it may miss some subnets. 

Is that the best way to it? If not, please advise