ntworld.ink← Networking toolsNETWORK LAB / 05

CONNECT · CONFIGURE · INVESTIGATE

LAN Builder

Build a network. Follow a packet. Understand the result.

A safe practice network

Everything happens in your browser.

YOUR CHALLENGE

To investigate

YOUR NETWORK

Devices & connections

Add

Select a device to configure it. Drag to arrange, or focus a device and use arrow keys. On a small screen, pan the diagram or use the device selector.

Start with a PC and a switch.Use the Add buttons above.
Ethernet Current frame Link down
Connect ports & inspect cables

One cable per port. Ethernet auto-MDIX is assumed; switches have eight ports and routers have three.

    PREDICT → TEST → EXPLAIN

    Follow the packet

    ARP + ICMP

    New tests start with empty ARP and MAC tables. A successful ping needs an Echo Request and an Echo Reply.

    No test yet

    READY TO INVESTIGATE

    What do you expect to happen?

    Choose two end devices and make a prediction. Then run ping and step through the decisions, Ethernet frames and return path.

    The highlighted devices and links follow the current step.

    Journey timeline

    1. Your test steps will appear here.
    Inspect learnt MAC and ARP tables at this step

    Switch MAC tables

    A switch learns the source MAC on the port where a frame arrives.

    ARP caches

    ARP maps an on-link IPv4 next hop to an Ethernet MAC address.

    Keep your network

    Changes are saved in this browser when storage is available.

    Copy or paste network data

    Use this fallback if your browser does not download files. Show your current network data, then copy it into a text file. Paste saved data here and choose Restore from data to reopen it.

    What this lab models

    Ethernet links, switch MAC learning, IPv4 LAN addressing (/1–/30), ARP and ICMP Echo in both directions. Routers use directly connected networks and longest-prefix selection. Frame transfer, ARP waiting and timing are simplified; displayed steps are a logical trace, not a real network capture.

    Ports act as auto-MDIX Ethernet. This lab does not model VLANs, spanning tree, static/dynamic routing protocols, DHCP, DNS, NAT, firewalls or Internet access. Redundant switch loops are rejected. A green ping proves only the simulated IP path, not application access.

    Prefer reduced motion? Your system preference is respected, and playback always starts paused. Use Next step to inspect changes at your own pace.