DHCP Smart Relay in EVPN-VXLAN
DHCP smart relay provides redundancy and resiliency to DHCP relay by allowing the relay agent to use multiple IP addresses as the gateway IP address. When forwarding DHCP client requests to a DHCP server, the relay agent initially uses the primary IP address as the gateway IP address. If the DHCP server does not respond with an offer message after three attempts, the relay agent repeats the process using an alternate IP address as the gateway IP address.
To use DHCP smart relay, you must have at least two IP addresses configured on the relay agent interface. If you configure more than two IP addresses on the relay agent interface, smart relay tries each IP address until an offer message is received.
DHCP smart relay is supported for EVPN over VXLAN in centrally routed bridging and edge-routed bridging modes. EVPN is usually configured with DHCP stateless relay to support multihoming, but DHCP smart relay is supported only for stateful relay. To support multihoming in an EVPN over VXLAN deployment with DHCP stateful relay, use the following configuration:
set forwarding-options dhcp-relay forward-snooped-clients all-interfaces set forwarding-options dhcp-relay overrides allow-snooped-clients set forwarding-options dhcp-relay route-suppression access-internal
To enable smart relay on all interfaces that are relay agents, configure the following statement:
set forwarding-options dhcp-relay overrides apply-secondary-as-giaddr
To enable smart relay on specific interfaces that are relay agents, configure the following statement:
set forwarding-options dhcp-relay group group-name interface interface-name overrides apply-secondary-as-giaddr