Where does Solr load balancer runs?

[Sreehareesh Kaipravan Meethaleveetil]

Hi,

I'm a little confused about the Solr replication/load balancing. Where exactly 
the load balancer runs, is it in the Master node (might not I guess) or Slave 
or somewhere else? Please let me know.

Thanks & Regards,
Sreehareesh KM