Main Mode and Quick Mode are different phases of the IKE Security
Association negotiation. Main Mode negotiates the security of the Quick Mode
negotiation and also does authentication (certificates, kerberos, preshared
key). Quick Mode negotiates the security methods and lifetime of the
Security Association that will be used to protect the traffic that matches
the Quick Mode filter. IPSECCMD tool lets you configure all the options that
affect the Main Mode and Quick Mode negotiations and subsequest SA's.
Soft associations (or soft SA's) are created when a machine has the option
"Allow unsecured communication with non-IPSec aware computers" is checked.
The machine first tries to negotiate a secure connection, but if the other
computer doesn't respond to its negotiation request then it will create a
Soft SA as a placeholder and communicate in the clear with the other
computer.
For more information read this article:
"Soft Associations" Between IPSec-Enabled and Non-IPSec-Enabled Computers
http://support.microsoft.com/default.aspx?scid=kb;en-us;234580