Refer to the exhibit.

 To enable communication between the subnets 192.168.1.0/24 and 172.18.1.0/24 using Cisco ACI fabric, it is necessary to configure the subnets appropriately. For option B, setting 172.18.1.0/24 as an External subnet for an external EPG under L3out_A allows it to be recognized as part of an external network, facilitating communication with other networks within the ACI environment. Similarly, for option D, configuring 172.18.1.0/24 with the Export Route Control scope under L3out_B ensures that this route is advertised out of L3out_B, allowing it to reach other network segments, including those connected via L3out_A where the subnet 192.168.1.0/24 resides. These configurations are crucial for proper routing between these two distinct subnets across the Cisco ACI fabric.

References := ( Implementing Cisco Application Centric Infrastructure Official Cert Guide )