A network technician is troubleshooting an issue where a newly deployed application server… — CompTIA Network+

A network technician is troubleshooting an issue where a newly deployed application server ( $10.40.20.50/24$ ) in VLAN 20 cannot connect to an off-site database cluster at $172.16.100.25/24$ . Hosts in VLAN 20 can reach local resources and the internet, but cannot communicate with the $172.16.100.0/24$ network. Following the standard CompTIA network troubleshooting methodology, place the diagnostic and remediation steps in the correct sequential order from first to last.

1Verify the application server's local IP configuration and test connectivity to its default gateway ( $10.40.20.1$ ) using ICMP echo requests.
2Execute a trace route command (`traceroute 172.16.100.25`) from the application server to identify the exact router hop where packet forwarding stops.
3Inspect the IP routing table (`show ip route`) on the gateway router to confirm an active static or dynamic route exists for destination network $172.16.100.0/24$ .
4Examine the active Access Control Lists (`show ip access-lists`) applied to the router's inbound and outbound interfaces for blocking rules or implicit deny drops.
5Apply the necessary ACL or route modification to the router configuration and verify full end-to-end database connectivity.

Answer

The correct sequential order for troubleshooting routing, gateway, and ACL issues is: 1) Verify local host configuration and gateway reachability (`item_1`), 2) Trace the path to locate the failure hop (`item_2`), 3) Check the router's routing table for destination routes (`item_3`), 4) Audit interface ACLs for filtering or implicit deny statements (`item_4`), and 5) Apply the configuration fix and verify end-to-end connectivity (`item_5`).

Following the structured CompTIA troubleshooting methodology, network diagnostics move logically from local host checks (ping default gateway), to path isolation (traceroute), to device routing tables (`show ip route`), to access control list inspection (`show ip access-lists`), and finally to implementing and verifying the solution.

Step-by-Step Solution

Test local stack and default gateway connectivity.

Confirms Layer 1–3 network interface functionality and local subnet communication.

Always eliminate local client and gateway configuration issues prior to inspecting remote network infrastructure.

Run path isolation diagnostics (`traceroute`).

Identifies the exact hop where packets are dropped.

Isolates whether the failure occurs within the local network, at a core routing boundary, or across a WAN/VPN link.

Verify routing table contents on the target router.

Determines if the router possesses a valid exit interface or next-hop route for

172.16.100.0/24

A missing route causes the router to drop packets or send them to an incorrect default route.

Audit interface Access Control Lists (ACLs).

Reveals whether traffic is permitted or inadvertently dropped by rule sequence or implicit deny.

Even with a valid route, interface ACLs evaluate traffic before or after routing lookup and can block communication.

Modify the configuration and conduct final verification.

Restores full connectivity and documents resolution.

Testing service reachability after applying configuration changes confirms complete problem resolution.

Key Concept

Structured Network Troubleshooting Methodology for Routing and ACLs

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