Centralized egress must provide a working bidirectional route chain through stateful NAT explains a different case, for example when a spoke VPC with a default route to Transit Gateway cannot reach the internet through central NAT because the egress VPC lacks the return path. In the current topology, the deciding factor is that gateway endpoints use route table prefix-list entries for supported regional AWS services; this choice therefore does not explain the specified remedy.

Gateway endpoint policies can constrain allowed AWS service operations over the endpoint route explains a different case, for example when a team wants to restrict S3 access through a gateway endpoint to specific buckets. In the current topology, the deciding factor is that gateway endpoints use route table prefix-list entries for supported regional AWS services; this choice therefore does not explain the specified remedy.

Private DNS can resolve supported public service hostnames to interface endpoint addresses explains a different case, for example when an interface endpoint exists but its private DNS alias is disabled and applications still resolve a public service address. In the current topology, the deciding factor is that gateway endpoints use route table prefix-list entries for supported regional AWS services; this choice therefore does not explain the specified remedy.

Flow logs report the action but not necessarily the exact rejecting rule explains a different case, for example when a flow log shows REJECT for a source and destination but a technician cannot tell which specific ACL caused it. In the current topology, the deciding factor is that network cost analysis needs service-level path and byte-volume attribution; this choice therefore does not explain the specified remedy.

Network path failures require examining each packet-filter and endpoint layer explains a different case, for example when an EC2 instance drops UDP while TCP works and a team assumes the security group must be the only blocker. In the current topology, the deciding factor is that network cost analysis needs service-level path and byte-volume attribution; this choice therefore does not explain the specified remedy.

An accepted network flow record does not guarantee a successful application response explains a different case, for example when a team sees ACCEPT records in VPC Flow Logs but an HTTPS application still times out. In the current topology, the deciding factor is that network cost analysis needs service-level path and byte-volume attribution; this choice therefore does not explain the specified remedy.

CloudTrail records control-plane API activity rather than every forwarded network packet explains a different case, for example when an organization wants retained proof of networking API configuration changes across AWS accounts. In the current topology, the deciding factor is that reachability Analyzer models AWS configuration paths and identifies blockers without creating test packets; this choice therefore does not explain the specified remedy.

VPC Flow Logs capture flow metadata rather than full application payloads explains a different case, for example when a VPC networking team needs metadata about accepted and rejected connections for an incident baseline. In the current topology, the deciding factor is that reachability Analyzer models AWS configuration paths and identifies blockers without creating test packets; this choice therefore does not explain the specified remedy.

Network Manager provides aggregate topology and route visibility for supported hybrid networking explains a different case, for example when a hybrid transit network has many attachments and needs a central view of route reachability and network events. In the current topology, the deciding factor is that reachability Analyzer models AWS configuration paths and identifies blockers without creating test packets; this choice therefore does not explain the specified remedy.

Gateway attachments and association permissions govern which VPC receives hybrid prefixes explains a different case, for example when a team configured a Direct Connect private VIF but selected the wrong AWS account's virtual private gateway. In the current topology, the deciding factor is that bGP session establishment requires compatible ASN and network peer configuration; this choice therefore does not explain the specified remedy.

A Direct Connect LAG aggregates eligible physical connections with defined compatibility rules explains a different case, for example when a network team builds a link aggregation group with circuits of incompatible speed or port location. In the current topology, the deciding factor is that bGP session establishment requires compatible ASN and network peer configuration; this choice therefore does not explain the specified remedy.

Dynamic routing convergence requires failure detection and withdrawing unusable next hops explains a different case, for example when a disaster recovery exercise shows VPN routes remain pinned to a removed data center after an appliance failure. In the current topology, the deciding factor is that bGP session establishment requires compatible ASN and network peer configuration; this choice therefore does not explain the specified remedy.

Assuming static VPN routing detects every remote CIDR change can blackhole traffic can be a real consequence when a customer VPN uses static routing while the team expects automatic failover after network changes. Here the relevant failure is that an up port without BGP routes leaves VPC address ranges unreachable. The alternative names a different failure mode and does not best account for the stated condition.

A VPC route toward the branch alone cannot deliver response packets back on premises can be a real consequence when a remote branch cannot reach AWS because its advertised VPC return prefix is absent from the corporate router. Here the relevant failure is that an up port without BGP routes leaves VPC address ranges unreachable. The alternative names a different failure mode and does not best account for the stated condition.

Restricting the protected CIDR set incorrectly can drop only the application traffic can be a real consequence when an on-premises firewall permits IPSec negotiation but blocks encapsulated user traffic after tunnel setup. Here the relevant failure is that an up port without BGP routes leaves VPC address ranges unreachable. The alternative names a different failure mode and does not best account for the stated condition.

Incorrect health checks can cause all service targets to be declared unhealthy can be a real consequence when a batch service runs healthy processes but fails ALB health checks because the probe path requires a user login. Here the relevant failure is that selecting an ALB for a non-HTTP custom protocol can be incompatible. The alternative names a different failure mode and does not best account for the stated condition.

Leaving one advertised zone without reachable healthy capacity can trigger client failures can be a real consequence when a multi-AZ target group shows one AZ unavailable when all targets there become unhealthy. Here the relevant failure is that selecting an ALB for a non-HTTP custom protocol can be incompatible. The alternative names a different failure mode and does not best account for the stated condition.

Changing DNS round-robin alone may not achieve the requested per-request controlled distribution can be a real consequence when a blue-green API deployment needs weighted HTTP routing to two target groups for a controlled release. Here the relevant failure is that selecting an ALB for a non-HTTP custom protocol can be incompatible. The alternative names a different failure mode and does not best account for the stated condition.

Flow-log ACCEPT alone can conceal a failed listener or wrong destination port can be a real consequence when a team sees ACCEPT records in VPC Flow Logs but an HTTPS application still times out. Here the relevant failure is that vPC Flow Logs cannot disclose full TCP flags and application payload content. The alternative names a different failure mode and does not best account for the stated condition.

A smooth long-window graph does not prove the absence of brief saturation can be a real consequence when a company is investigating short bursts of traffic that disappear from five-minute aggregated metrics. Here the relevant failure is that vPC Flow Logs cannot disclose full TCP flags and application payload content. The alternative names a different failure mode and does not best account for the stated condition.

A stateful security group allow rule cannot compensate for stateless NACL denial can be a real consequence when an EC2 instance drops UDP while TCP works and a team assumes the security group must be the only blocker. Here the relevant failure is that vPC Flow Logs cannot disclose full TCP flags and application payload content. The alternative names a different failure mode and does not best account for the stated condition.

Coarse geographic rules without testing can deny legitimate travelers or global partners can be a real consequence when a production ALB must accept only approved client geographies under documented policy while retaining measured business exceptions. Here the relevant failure is that a transparent proxy alone cannot enforce policy against traffic that never traverses it. The alternative names a different failure mode and does not best account for the stated condition.

A matching alert alone does not stop prohibited traffic from reaching its target can be a real consequence when a finance environment uses AWS Network Firewall but the rule group is set to log-only while policy requires blocking. Here the relevant failure is that a transparent proxy alone cannot enforce policy against traffic that never traverses it. The alternative names a different failure mode and does not best account for the stated condition.

Unnecessary broad inbound SG rules allow new unwanted connections, not just replies can be a real consequence when a network engineer opens all ephemeral ports inbound in a security group believing return packets require explicit permits. Here the relevant failure is that a transparent proxy alone cannot enforce policy against traffic that never traverses it. The alternative names a different failure mode and does not best account for the stated condition.

Centralized conditional forwarding can reduce inconsistent duplicated DNS configurations explains a different case, for example when a private application needs one coherent DNS resolution path from many shared-network VPCs to corporate systems. In the current topology, the deciding factor is that dNS delegation transfers authority through NS records rather than duplicating every child A record; this choice therefore does not explain the specified remedy.

Hybrid DNS routing decisions depend on matching names and rule scope rather than alphabetical order explains a different case, for example when two private hosted zones share a suffix and a resolver rule has a more-specific matching domain. In the current topology, the deciding factor is that dNS delegation transfers authority through NS records rather than duplicating every child A record; this choice therefore does not explain the specified remedy.

Positive DNS response caching persists for the TTL observed before a change explains a different case, for example when a web administrator changed a DNS record but some users still reach an old destination for several minutes. In the current topology, the deciding factor is that dNS delegation transfers authority through NS records rather than duplicating every child A record; this choice therefore does not explain the specified remedy.

Increasing instance CPU cannot fix a shorter intermediary idle timeout can be a real consequence when a long-running upload behind an ALB is cut off after idle periods although the target process stays alive. Here the relevant failure is that making the endpoint internet-facing violates the private-network requirement. The alternative names a different failure mode and does not best account for the stated condition.

Changing DNS round-robin alone may not achieve the requested per-request controlled distribution can be a real consequence when a blue-green API deployment needs weighted HTTP routing to two target groups for a controlled release. Here the relevant failure is that making the endpoint internet-facing violates the private-network requirement. The alternative names a different failure mode and does not best account for the stated condition.

Manually editing generated ALB listeners outside the controller may be overwritten can be a real consequence when an EKS platform needs Kubernetes Ingress-driven creation of an ALB across cluster namespaces. Here the relevant failure is that making the endpoint internet-facing violates the private-network requirement. The alternative names a different failure mode and does not best account for the stated condition.

Keep routing changes with the VPC owner and allocate permitted participant resource privileges would address a different scenario, such as when an AWS organization has a shared VPC but a participant account cannot edit the subnet route table it does not own. The present issue requires add the intended principal to the endpoint service allow list and approve pending connections as required because the network path and control point are different; the alternative does not directly meet this requirement.

Make forward and return Transit Gateway and VPC routes symmetric around stateful inspection would address a different scenario, such as when an EKS application connects to a private database through Transit Gateway but replies take a different uninspected route. The present issue requires add the intended principal to the endpoint service allow list and approve pending connections as required because the network path and control point are different; the alternative does not directly meet this requirement.

Share Transit Gateway through RAM and enforce attachment acceptance and identity policy would address a different scenario, such as when a central networking account wants to accept VPC attachments from member accounts without granting them full gateway administration. The present issue requires add the intended principal to the endpoint service allow list and approve pending connections as required because the network path and control point are different; the alternative does not directly meet this requirement.