currently is
centos1 nginx1 + keepalived master
centos2 nginx2 + keepalived backup
centos3 is not equipped with anything
the domain name is resolved to the IP of centos1.
VIP is the IP, of centos1, but vip doesn"t know what to modify.
now when the nginx and keepalived, access domain names of centos1 are turned off, it seems that centos2 is not connected