Passed Exam Today NSE7_CDS_AR-7.6

Comprehensive and Detailed Explanation From FortiOS 7.6, FortiWeb 7.4 Exact Extract study guide:

In an AWS SD-WAN Transit Gateway (TGW) Connect topology, traffic flow must be meticulously orchestrated through VPC route tables to ensure that the FortiGate-VM (Security VPC) can inspect traffic transitioning between spokes.

Spoke to TGW Redirection (Option E): For traffic to leave a Spoke VPC and reach the inspection hub, the Spoke VPC internal routing table must be configured to send all non-local traffic (0.0.0.0/0) to the Transit Gateway (TGW). This is the first step in the traffic chain.

TGW to FortiGate Redirection (Option A): Once the traffic arrives at the TGW and is forwarded to the Security VPC via a TGW attachment, it lands in the TGW subnet (or attachment subnet). To ensure this traffic is inspected, the Security VPC TGW subnet routing table must point the default route (0.0.0.0/0) to the FortiGate's internal network interface (ENI).

FortiGate Return/Egress Path (Option D): After the FortiGate processes the packet, it must be sent back to the TGW to reach its final destination in a different spoke or to exit via a different gateway. Therefore, the Security VPC FortiGate internal subnet routing table (the subnet where the FortiGate's internal leg resides) must have a default route (0.0.0.0/0) pointing back to the TGW.

Why other options are incorrect:

Option B: If the Security VPC TGW subnet routing table points to the TGW as the next hop, it creates a routing loop where traffic arrives from the TGW and is immediately sent back without being inspected by the FortiGate.

Option C: Pointing all traffic to an Internet Gateway (IGW) would bypass the Transit Gateway entirely and send traffic to the public internet rather than through the internal security fabric.

Comprehensive and Detailed Explanation From FortiOS 7.6, FortiWeb 7.4 Exact Extract study guide:

According to the FortiOS 7.6 Azure Administration Guide and the Fortinet 7.4 Public Cloud Security documentation regarding Azure Virtual WAN (vWAN) architectures, the choice of connectivity depends on the required performance, security, and scale:

ExpressRoute (Option D): For a large-scale enterprise deployment involving a company headquarters and multiple branch sites, ExpressRoute is the "best" and most robust solution. It provides a private, dedicated, and high-throughput connection (up to 100 Gbps) that bypasses the public internet entirely. This ensures predictable low latency and higher reliability compared to internet-based tunnels.

Virtual WAN Integration: Azure vWAN Standard SKU explicitly supports ExpressRoute gateways as a primary connectivity method for on-premises sites. This allows the vWAN hub to act as a global transit point, seamlessly connecting the ExpressRoute-linked headquarters to other branch sites and VNET spokes.

Scalability for Headquarters: While site-to-site IPsec VPNs are common for smaller branches, the "main company site" or headquarters typically requires the high bandwidth and SLA guarantees provided by ExpressRoute.

Why other options are incorrect:

Option A & B: L2TP and SSL VPN are primarily used for remote user access (Point-to-Site) rather than permanent site-to-hub infrastructure connections. vWAN uses OpenVPN or IKEv2 for user VPNs, not L2TP.

Option C: While GRE tunnels are used in some networking scenarios, they are not a native, primary gateway connectivity option for the Azure vWAN hub compared to the standardized Site-to-Site VPN (IPsec) and ExpressRoute.