Sateesh
Within a GSS network both GSS will have the same DNS rule. SO if DNS request hits any of the GSS it will get the similar result.
When you delegate subdomain to two GSSs then any of the GSS can get hit.
What you could achieve is that Any of the GSSs should respond with VIP at DC1 only. Only if VIP at DC1 is not available (DC1 is down ) then both GSSs should serve A-record of VIP at DC2.
In order to achieve this you will need to create VIP type Answers for both DCs and group them in an Answer group.
In DNS rule select this answer group and select ordered list as the load balancing algo
(Assign lower order value to the prefered answer)
for example if you assign 1 to DC1 Answer & order 2 to DC2 answer then GSS will server Answer1 and will only server answer 2 if ANswer1 is offline.
Weight is used for weighted roundrobin algo.
For example if you want GSS to reply with Answer1 to first request & Answer2 to next two requests then you will assign weight1 to Answer1 & Weight2 to Answer2.You will also need to select roundrobin as algo to make it work.
Syed Iftekhar Ahmed
