You need to secure communications from a mobile command center which uses a 5G mobile...

The correct answers are A and D. A mobile command center using a 5G ISP behind CGNAT is operating behind dynamic address translation. For IPsec to work reliably through NAT, the SRX must support NAT Traversal, which encapsulates IKE and ESP traffic in UDP/4500 after NAT is detected. Juniper states that NAT-T is used when NAT devices exist in the datapath and that NAT keepalives are required because NAT devices age out UDP translations. Juniper’s Security Director VPN workflow also specifically says to enable NAT-T when the dynamic endpoint is behind a NAT device.

DPD is also required because mobile and carrier-grade NAT connections can disappear, roam, or become stale without a clean tunnel teardown. Juniper defines Dead Peer Detection as the method used by IPsec peers to verify whether the remote peer is still present and responsive by sending encrypted IKE notification payloads and waiting for acknowledgements. Option B is not the best answer because IKEv1 aggressive mode is weaker and does not provide identity protection; Juniper also notes that aggressive mode applies only to IKEv1. Option C is invalid because IKEv2 aggressive mode does not exist. Reference topics: IPsec VPN, NAT-T, CGNAT, dynamic endpoints, DPD, IKE peer availability.