Virtual LAN (VLAN)
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Scenario 1 — Flat network in one subnet
1. What it shows (logical):
Single switch (Sw1) with two PCs in the same IP subnet (e.g. 192.168.1.0/24). They are in the same broadcast domain and will communicate L2→L3 locally.
2. Goal:
Show two hosts in same VLAN/subnet communicating without routing.
3. Expected behavior:
Hosts exchange ARP and then IP traffic without any router involvement.
Scenario 2 — Two subnets on same switch (no routing)
1. What it shows:
Same physical switch, but the two PCs are configured with different IP subnets (e.g. 192.168.1.0/24 and 192.168.2.0/24). They are still in the single L2 domain, but IP layer says they’re on separate networks → they cannot communicate unless there is an L3 device (router).
2. Why ping fails:
When PC1 wants to send to PC2 (192.168.2.100) it determines the destination is off-subnet → it ARPs for its configured default gateway. If no router is present at .1, or gateway is not configured, ARP fails and packets never reach PC2.
Scenario 3 — Physical separation
1. What it shows:
Two physically separate switches (Sw1 and Sw2), each with a local PC in different subnets. There is physical separation — i.e., they are not connected or are not trunked, so they are separate L2 domains.
2. Key ideas:
Physical separation is one way to isolate broadcast domains (security/traffic containment).
If the two networks need to communicate, you must connect them via an L3 device (router) or interconnect switches and trunk VLANs appropriately.
Scenario 4 — VLANs — logical separation on one physical switch
1. What it shows:
One physical switch is logically split into two VLANs (VLAN 1 and VLAN 2). Each PC is on a different VLAN/subnet. This reproduces the same effect as physically separate switches, but with one physical switch.
2. Goal:
Create VLANs, place ports into VLANs, test intra-VLAN comms and inter-VLAN routing.
Cisco Packet Tracer (Version 6.2.0.0052)
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Keywords
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