On Juniper devices acting as DHCP server, static reservation (static lease based on MAC address) can be achieved as followed :
set access address-assignment pool <dhcp-pool-name> family inet host <client-host-name> hardware-address <client-mac-address> ip-address <client-static-ip>
Example :
set access address-assignment pool DHCP_Grp_v128_Pool1 family inet host mtrlpqm1lt0276 hardware-address 8c:ae:4c:c8:45:c5 ip-address 10.10.128.72
Then apply the configuration :
commit
(or using “commit synchronize” with virtual-chassis configuration)