DHCP - isc dhcpd server - failover

Hi, I try config package isc-dhcp-serve like
slave dhcp server
but every change turris up like slave
dhcpd server frezz
my config;

failover peer “dhcp-failover” {
secondary; # declare this to be the primary server
address “my ip”;
port 647;
peer address “master ip server”;
peer port 648;
max-response-delay 30;
max-unacked-updates 10;
load balance max seconds 3;