In local mode, the IAP cluster at the branch office has a local subnet and the master IAP of the cluster acts as the DHCP server and gateway for clients. The local mode provides access to the corporate network using the inner IP of the IPsec tunnel. The local mode is recommended for this scenario because it allows the branch office to remain functional even if the link to the main office fails, as the clients can still obtain IP addresses and access local resources. The local mode also avoids the need for additional routing or switching configuration on the MC or the branch office network12. References:

1: Understanding IAP-VPN Architecture - Aruba

2: IAP-VPN Forwarding Modes - Aruba