Dell EMC SmartFabric OS10 User Guide Release 10.5.1

Option 82 for security

DHCP, as defined by RFC 2131, provides no authentication or security mechanisms. To ensure security, the DHCP relay agent supports Option-82 with the Circuit ID sub-option, which is the printable name of the interface where the client request was received.

This option secures all DHCP traffic that goes through a DHCP relay agent, and ensures that communication between the DHCP relay agent and the DHCP server is not compromised.

The DHCP relay agent inserts Option 82 before forwarding DHCP packets to the DHCP server. The DHCP server includes Option 82 back in its response to the relay agent. The relay agent uses this information to forward a reply out the interface on which the request was received rather than flooding it on the entire VLAN. However, the relay agent removes Option 82 from its DHCP responses before forwarding the responses to the client.