NetScaler Perform the following steps to select SNIP 

Step-1: Checking NetScaler route table with destination Server IP address, decided to pick up a "Directly connected routes entry" or "Remote routes entry" referring Longest prefix match rules.
Step-2: NetScaler list the SNIP within the same network segment as route entry.

• If multiple SNIPs are listed Step-2, NetScaler will randomly select one to build connection with backend server. 
• To control SNIP selection, apply the netprofile in NetScaler, following the KB article（NetScaler netprofile)