AZ-802: Administering Windows Server

A DHCP scope is an administrative grouping of IP addresses for the computers on one subnet that the DHCP server can lease, and a subnet can have only a single scope with one continuous address range, so a server that services a routed network is configured with one scope per IPv4 subnet it addresses: the two client VLAN subnets plus the datacenter VLAN subnet the server is deployed into, for three scopes. Devices on a subnet that must keep manually assigned addresses -- the DHCP server itself, routers, and other infrastructure -- are accommodated with an exclusion range inside that subnet's scope rather than by leaving the subnet without a scope. DHCP relay agents are required only where clients and the server are separated by a router: DHCPDISCOVER and DHCPREQUEST are subnet-local broadcasts that routers do not forward, so every subnet that does not host the DHCP server needs a relay agent (an IP helper on that subnet's router interface) to forward the broadcast to the server as a unicast and to stamp the gateway address the server uses to select the matching scope. Only the two client VLANs are remote from the datacenter VLAN, so two relay agents are needed and none is required on the datacenter VLAN itself.