Scanning Class A network

[tarunthenut () gmail com]

Hello All,
 Recently I was given a task to carry out a port scan of an entire valid
Class A range (Dont ask me what the huge pool of valid IP's was for  :)  ).
The scan needed to be carried out externally, and not from within the
network to identify hosts and ports exposed to the Internet.
 The problem compounded cause of the following limitations :
1. ICMP was not allowed in the network
2. The IP range was to be scanned every month for the entire port range fro=
m
1-65535 for TCP & UDP
 After searching for a suitable scanner which could scan such a large range
in reasonable time, I could think of only nmap, nessus, superscan and ISS.
 But because of the limitations stated above,all the tools took a huge
amount of time (ran into month).
 I have struggled with options within the tools, tried configurable
parameters (host time out, parallelism, RTT etc) and divided into smaller
class C networks and scanned.but still the scan seems to take ages even if
it is
 Any advise would be welcome  :) 
 
Cheers
 tarunthenut

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