From: http://krypted.com/tag/smb/

  Basic Scanning
  To then scan a computer, just use the mmap command followed by the host name or 
  even throw a -v option in there to see more information (you can use a hostname 
  or an IP):  nmap -v www.apple.com
  Use the -6 option if scanning via IPv6:
  nmap -v -6 8a33:1a2c::83::1a
  Firewalls
  Next, we’ll look at trying to bypass pesky annoyances like stageful packet inspection on 
  firewalls. First, check whether there is actually a firewall using -s:
  nmap -sA www.apple.com 
  Scan even if the host is protected by a firewall: 
  nmap -PN www.apple.com
  Just check to see if some devices are up even if behind a firewall:
  nmap -sP 192.168.210.10-20