The scenario
Core Switch has five ports in use, and every one is an access port. sw1 (Sales PC), sw3 (VLAN Router ge0) and sw4 (Sales Printer) are in VLAN 10; sw2 (Eng PC) and sw5 (VLAN Router ge1) are in VLAN 20. Each VLAN is its own Layer 2 segment, as if the switch were two separate switches. Sales uses 10.10.10.0/24 and Engineering 10.20.20.0/24. VLAN Router has one cable into each VLAN, ge0 = 10.10.10.1 and ge1 = 10.20.20.1, and routes between them. Sales PC and Eng PC use it as their default gateway; Sales Printer has no gateway.
What you will work out
See how access VLANs divide one physical switch into separate Layer 2 segments, and how a router connects them.
Why this matters
VLANs let one set of switches carry separate networks for staff, guests, phones, cameras or servers, with a router or firewall deciding what may cross between them. A port in the wrong VLAN gives you a device with a correct address and a link light that still reaches nothing, and the fix is on the switch, not the device: show vlan brief on a Cisco switch, or bridge vlan show on Linux, lists each port's VLAN.
Running it
VLANs: Network Segmentation opens on a canvas, already wired and addressed. Trace a packet through it hop by hop, or run the same topology live on real Linux network namespaces. How the two modes differ.
Open VLANs: Network Segmentation
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