Tools to check network vulnerability ???

[rico_hao40]

Anydoby advise some tools to discover the network vulnerability ? like nmap.

I use nmap to scan one of my networks, I got one message

"TCP Sequence Prediction: Difficulty=258 (Good luck!)"

what's that mean, is is good ?

[cisco24x7]

I use Nessus for OpenSource.

For comercial products, I use Qualys (Cisco

Partner) or another product from Spirent.

CCIE Security