Exam 300-620 topic 1 question 205 discussion

Unicast Routing: If this setting is enabled and a subnet address is configured, the fabric provides the default gateway function and routes the traffic. Enabling unicast routing also instructs the mapping database to learn the endpoint IP-to-VTEP mapping for this bridge domain. The IP learning is not dependent upon having a subnet configured under the bridge domain. https://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/2-x/L3_config/b_Cisco_APIC_Layer_3_Configuration_Guide/b_Cisco_APIC_Layer_3_Configuration_Guide_chapter_010.html

The Layer 3 Configurations tab of the bridge domain panel allows the administrator to configure the following parameters: Unicast Routing: If this setting is enabled and a subnet address is configured, the fabric provides the default gateway function and routes the traffic. Enabling unicast routing also instructs the mapping database to learn the endpoint IP-to-VTEP mapping for this bridge domain. The IP learning is not dependent upon having a subnet configured under the bridge domain. Subnet Address: This option configures the SVI IP addresses (default gateway) for the bridge domain. Limit IP Learning to Subnet: This option is similar to a unicast reverse-forwarding-path check. If this option is selected, the fabric will not learn IP addresses from a subnet other than the one configured on the bridge domain. Unicast Routing feature in ACI allows the Leaf Switches to learn the IP addresses associated with the Endpoint which are connected to ACI Fabric. The Unicast Routing feature also enables IP Routing under the bridge domain ( Similar to IP Routing Command in Nexus-OS/ Catalyst OS).