thanks johan,
I am currently using one dhcp in our environment need to change his ip address.what is command to change dhcp server ip address.
after changing the dhcp ip address all vlan by default take ip address from the new dhcp server.
its not required to use enable bootprelay commands for all vlan .because i have already enable bootprelay commands for all vlan.
my current config_
configure bootprelay add vr VR-Default
configure bootprelay dhcp-agent information check vr VR-Default
enable bootprelay vr VR-Default vlan