Hi, I am new to nginx, and I wanna know the difference between
upstream backend {
ip_hash;
server backend1.example.com;
server backend2.example.com;
server backend3.example.com down;
}
and
upstream backend {
server backend1.example.com;
server backend2.example.com;
server backend3.example.com down;
ip_hash;
}

Thanks in advance!