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RUSSELL EVERSON · INTERACTIVE NETWORK LAB

Follow a Network Packet

See how a browser finds a website, crosses a firewall, and receives a reply. Then introduce a DNS failure and troubleshoot it.

Educational simulation · No real network traffic
Windows client192.168.50.100 · illustrative
DC01 · DNS192.168.50.10
OPNsenseGateway · 192.168.50.1
InternetRemote destination
Ready to trace a connection

Choose a destination and click Send Packet. DNS resolves the name first; the website traffic then uses the gateway.

    Try the troubleshooting challenge

    Click Break DNS, then send a packet to the website name. Next, choose Direct IP connectivity test and send again. What does the difference tell you?

    Reveal the diagnosis

    If direct IP connectivity works while name resolution fails, investigate DNS: the client’s configured resolver, the DNS service, reachability, and records. This is a clue, not proof that every other network service is healthy.

    What this simulation simplifies

    DNS is a separate query and response, not a router that website traffic passes through. DC01 may answer from cache or ask an upstream resolver. The firewall applies rules and performs source NAT before traffic reaches the internet. Return traffic follows the connection’s state.

    The direct IP option represents a basic connectivity check, not an HTTPS website request. Real HTTPS sites can require a hostname for certificate validation and virtual hosting. ARP, TCP handshakes, TLS, and upstream hops are omitted here.

    Built to demonstrate DNS troubleshooting, default gateways, firewall rules, and NAT in a VirtualBox lab.