The firewall can act as a DHCP-server.

Example:

#> show configuration system services dhcp-local-server
group office {
interface reth0.244;
}
group eduroam {
interface reth0.249;
}
group printers {
interface reth0.246;
}
requested-ip-interface-match;

Example of a pool:

#> show configuration access address-assignment 
pool office {
family inet {
network 10.20.0.0/23;
range clients {
low 10.20.0.40;
high 10.20.1.250;
}
dhcp-attributes {
maximum-lease-time 3600;
domain-name some.domain.name;
name-server {
89.32.32.32;
8.8.8.8;
}
router {
10.20.0.1;
}
}
##### Below is how to set a fixed address for an equipment #####
host test-pc-01 {
hardware-address ab:cd:ef:01:02:03;
ip-address 10.20.0.20;
}
}
}