Preferred IP is NULL

[Anuj Wadehra]

Hi,
We use multiple interfaces in multi DC setup.Broadcast address is public IP 
while listen address is private IP.
I dont understand why prefeerred IP in peers table is null for all rows.
There is very little documentation on the role of preferred IP and when it is 
set. As per code TCP connections use preferred IP. According to my 
understanding, nodes in local dc should use preferrably private IP to connect 
and that's referred as preferred IP for a node.
Setup: Cassandra 2.0.14
ThanksAnuj