Hello,
Question: "But does it work with the second IP address on the client or not? or only the first IP address?"
Answer: Yes, It works with the Second IP address on the client as when the client is moving out of the network, it is the second IP in use.
You can identify the location based on IP addresses, WINS, DHCP, or DNS server addresses, network connections, and other criteria.
However, incase if you want another IP address, then you could do the necessary changes in MSL.
Check this Article below:
Managed Load Balancing: Setting up Management Server Lists based on locations in Symantec Endpoint Protection Manager.
http://www.symantec.com/docs/TECH104582
Managing locations for remote clients
http://www.symantec.com/docs/HOWTO55419
Video: https://www-secure.symantec.com/connect/videos/location-awareness
Hope that helps!!