What is a DHCP relay agent (IP helper address), and why is it necessary in a routed network with multiple VLANs?

• A.A DHCP relay agent is only needed for IPv6; IPv4 DHCP works across routers without any configuration
• B.DHCP uses broadcast (destination 255.255.255.255) for Discover and Request messages; routers do not forward broadcasts. A DHCP relay agent (configured with 'ip helper-address' on the VLAN interface) intercepts broadcast DHCP messages on the local VLAN and forwards them as unicast UDP packets to the DHCP server's IP, enabling one central DHCP server to serve all VLANs
• C.A DHCP relay agent encrypts DHCP traffic between clients and servers to prevent snooping on untrusted VLANs
• D.A DHCP relay agent is a redundant DHCP server that activates when the primary DHCP server is unreachable