Correct Answer B Once the border leaf learns the external routes, it can then redistribute the external routes of a given VRF instance to an MP-BGP address family (VPNv4 or VPNv6). MP-BGP maintains a separate BGP routing table for each VRF instance. Within MP-BGP, the border leaf switch advertises routes to a spine switch, which is a BGP route reflector. The routes are then propagated to all the leaf switches where the VRF instances are instantiated. https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/guide-c07-743150.html

Shouldn't this be A? We are not talking transit routing here...

Correct Answer:B.

Its actually under Route Control Enforcement , profile so its simply A

In Cisco ACI, a border leaf node on which Layer 3 Outsides (L3Outs) are deployed redistributes L3Out routes to the BGP IPv4/IPv6 address family and then to the MP-BGP VPNv4/VPNv6 address family along with the VRF information so that L3Out routes are distributed from a border leaf node to other leaf nodes through the spine nodes. Interleak redistribution in the Cisco ACI fabric refers to this redistribution of L3Out routes to the BGP IPv4/IPv6 address family. By default, interleak happens for all L3Out routes, such as routes learned through dynamic routing protocols, static routes, and directly-connected subnets of L3Out interfaces, except for routes learned through BGP. Routes learned through BGP are already in the BGP IPv4/IPv6 table and are ready to be exported to MP-BGP VPNv4/VPNv6 without interleak. https://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/5-x/l3-configuration/cisco-apic-layer-3-networking-configuration-guide-50x/route-control-50x.html

To redistribute externally learned OSPF routes within the Cisco ACI fabric, you need to configure a Route Control Profile. This profile is used to control the import and export of routes between different routing protocols or instances within the ACI fabric, including the redistribution of routes from external sources such as OSPF into the ACI fabric's routing protocol

B - Distribute external routes within the ACI fabric ACI uses Multi-Protocol BGP (MP-BGP) with VPNv4 in the ACI infra VRF (overlay-1 VRF) to distribute external routes from a border leaf to other leaf switches. Similar to other configurations/components in the ACI infra VRF such as ISIS between each switch, this configuration is also automated in the background. The only two configurations that users need to perform are as follows: ● Select the BGP AS number. ◦ This is the AS number to represent the entire ACI fabric. It is used for infra MP-BGP between leaf and spines, and for BGP in user L3Outs to establish BGP peers with external devices. ● Select spine switches as BGP Route Reflectors. ◦ Each leaf switch will be a BGP client for the selected route-reflector spine switches. https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/guide-c07-743150.html

Its B 2. Distribute external routes within the ACI fabric ACI uses Multi-Protocol BGP (MP-BGP) with VPNv4 in the ACI infra VRF (overlay-1 VRF) to distribute external routes from a border leaf to other leaf switches. Similar to other configurations/components in the ACI infra VRF such as ISIS between each switch, this configuration is also automated in the background. The only two configurations that users need to perform are as follows: ● Select the BGP AS number. ◦ This is the AS number to represent the entire ACI fabric. It is used for infra MP-BGP between leaf and spines, and for BGP in user L3Outs to establish BGP peers with external devices. ● Select spine switches as BGP Route Reflectors. https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/guide-c07-743150.html