From what I can tell it is a broad stroke tool that associates packets with subnet source as the vlan.  Here is a couple articles that I gathered on the subject.  The User Guide and CLI Guide for the 62xx switch does not elaborate on the vlan association subnet command. www.simulationexams.com/.../types-of-vlans.htm itknowledgeexchange.techtarget.com/.../bind-ip-subnet-to-vlan-in-dell-l3-switch  <ADMIN NOTE: Broken link has been removed from this post by Dell> How are you putting 2 IPs on the same workstation?  Does it have a dual port nic?  If so then you would have 2 cables going to different ports on the switch correct?
What's the difference between these two CLI commands? 
Creating VLANs and assigning subnets question