Even after closing clients, I can see the dead connections when I run the command from redis server
command: netstat -ano | find
I could not see any configuration to do 'keep alive' check in sentinel.
what could be the problem.
I don't know what you mean by Sentinel Dead Peers but if you're asking why there's connections are open after you dispose the client you're likely using a Connection Pool where disposing clients just return the open clients to the pool.
If you have any questions about Redis server or sentinel processes themselves you can ask them on the Redis Mailing List.