VPC routing selects the most specific matching destination; a broader transit route cannot displace the direct local destination range; those conditions do not produce the required result: explain more-specific TGW route selection.

TGW evaluates the route table associated with the inbound attachment; having a destination attached elsewhere is insufficient if that route table lacks a matching path; the operational gap would remain because the question requires a way to explain more-specific TGW route selection.

TGW route tables act only after traffic enters the transit gateway; the source VPC route table must first select the transit gateway as next hop for the destination prefix; it is not the action that directly makes the system explain more-specific TGW route selection.

AWS Config records supported resource configuration changes and can evaluate guardrails over time; CloudWatch connection metrics do not preserve the resource's compliance timeline; it changes a different aspect of the architecture rather than fulfilling the need to distinguish AWS routing from host-level refusal.

Resolver forwarding generates DNS queries from the endpoint ENIs; restrictive security-group egress and return-path routing can prevent a valid forwarding rule from delivering them; the operational gap would remain because the question requires a way to distinguish AWS routing from host-level refusal.

Flow Logs classify traffic as accepted or rejected at the interface-level logging view; they do not directly name the exact security-group or NACL rule responsible; that still would not establish the requested outcome: distinguish AWS routing from host-level refusal.

AWS Config records supported resource configuration changes and can evaluate guardrails over time; CloudWatch connection metrics do not preserve the resource's compliance timeline; the operational gap would remain because the question requires a way to differentiate existing flows from new security-group flows.

Managed prefix lists can keep approved CIDR collections current for supported AWS services, reducing manually maintained broad address rules in eligible security-group configurations; it is not the action that directly makes the system differentiate existing flows from new security-group flows.

Flow Logs classify traffic as accepted or rejected at the interface-level logging view; they do not directly name the exact security-group or NACL rule responsible; that still would not establish the requested outcome: differentiate existing flows from new security-group flows.

The IPv4 fragmentation-needed message is part of IPv4 PMTUD; IPv6 relies on its own control message because routers do not fragment IPv6 packets.

Echo Request helps with ping reachability checks but does not tell a sender which packet size exceeds the path MTU.

A TCP reset terminates the transport connection rather than telling the IPv6 sender which packet size can traverse the path. IPv6 Path MTU Discovery relies on ICMPv6 Packet Too Big feedback.

Local preference is normally considered before AS-path length within an AS; changing path length alone may not override a deliberately preferred route; the scenario instead needs an action that will find an overriding subnet route.

BGP exchanges prefixes and responds to route withdrawals across the VPN tunnel; static routing requires explicit configuration and does not provide equivalent dynamic route signaling; those conditions do not produce the required result: find an overriding subnet route.

With an eligible VGW attachment, route propagation can install learned remote prefixes into the selected VPC route tables; merely establishing the tunnel does not make every subnet route table use those routes; it changes a different aspect of the architecture rather than fulfilling the need to find an overriding subnet route.

BGP neighbors must agree on each other's peer ASNs; a functioning physical circuit and VLAN cannot establish the control-plane adjacency when the remote AS is configured incorrectly; the scenario instead needs an action that will diagnose physical transport behind BGP flaps.

Restricting advertised prefixes keeps hybrid routing within the intended enterprise reachability boundary; unnecessary default route advertisements can attract traffic not meant for Direct Connect; those conditions do not produce the required result: diagnose physical transport behind BGP flaps.

A BGP peer can stay reachable while a router enforces prefix limits or suppresses updates; diagnosing the actual routes received and the configured threshold avoids misclassifying the event as link failure; the operational gap would remain because the question requires a way to diagnose physical transport behind BGP flaps.

PSK rotation changes tunnel authentication material; routing policies and BGP prefixes can remain logically independent while tunnel reestablishment must be planned; those conditions do not produce the required result: restore matching VPN tunnel authentication.

Customer gateways should use the actual tunnel outside addresses supplied for the VPN connection and plan for documented endpoint changes; fixed assumptions about future endpoints create outages; it changes a different aspect of the architecture rather than fulfilling the need to restore matching VPN tunnel authentication.

BGP exchanges prefixes and responds to route withdrawals across the VPN tunnel; static routing requires explicit configuration and does not provide equivalent dynamic route signaling; it is not the action that directly makes the system restore matching VPN tunnel authentication.

Reducing churn and spreading simultaneous destination flows can mitigate per-tuple ephemeral-port pressure; simply adding unrelated DNS records does not create more NAT port capacity; it changes a different aspect of the architecture rather than fulfilling the need to diagnose NAT source-port exhaustion.

A successful handshake uses small packets; oversized encrypted data packets may be fragmented or dropped, so an appropriately sized MSS avoids black-hole behavior along the limiting hop; the operational gap would remain because the question requires a way to diagnose NAT source-port exhaustion.

Matching each workload AZ to a local NAT gateway avoids forcing routine egress through another AZ and removes one AZ's gateway as a shared dependency, though gateway hourly costs increase; that still would not establish the requested outcome: diagnose NAT source-port exhaustion.

Network ACLs evaluate stateless rules in ascending number order and support explicit denies; security groups do not have deny rules; Both ingress and egress paths still need compatible NACL handling; the operational gap would remain because the question requires a way to diagnose path changes after a managed prefix-list update.

Managed prefix lists can keep approved CIDR collections current for supported AWS services, reducing manually maintained broad address rules in eligible security-group configurations; that still would not establish the requested outcome: diagnose path changes after a managed prefix-list update.

Security groups are stateful, but replacing the rules does not grant indefinite access for new flows; connection tracking and subsequent connection establishment follow allowed traffic and rule state; the scenario instead needs an action that will diagnose path changes after a managed prefix-list update.

A /24 destination route is more specific than a /16 and governs traffic to addresses in that range, regardless of broad propagation from another attachment; that still would not establish the requested outcome: explain local-route precedence over a summary.

TGW route tables act only after traffic enters the transit gateway; the source VPC route table must first select the transit gateway as next hop for the destination prefix; the scenario instead needs an action that will explain local-route precedence over a summary.

TGW evaluates the route table associated with the inbound attachment; having a destination attached elsewhere is insufficient if that route table lacks a matching path; those conditions do not produce the required result: explain local-route precedence over a summary.

Security groups are stateful, but replacing the rules does not grant indefinite access for new flows; connection tracking and subsequent connection establishment follow allowed traffic and rule state; the scenario instead needs an action that will identify the actual filter denying a flow.

AWS Config records resource configuration and can evaluate it against guardrails; a workflow can then notify or trigger controlled remediation; those conditions do not produce the required result: identify the actual filter denying a flow.

Network ACLs are stateless, so permitting an inbound destination port does not automatically permit the corresponding outbound return packet to a client-chosen port; it changes a different aspect of the architecture rather than fulfilling the need to identify the actual filter denying a flow.