Configure a network by hand in Cisco IOS — VLANs and trunking, inter-VLAN routing, spanning tree and EtherChannel, static routing and HSRP, OSPF, BGP, and ACLs with NAT. Build the topology in a free simulator and paste each config in as you go.
Before you start
You need a network simulator to run the configs — free options are Cisco Packet Tracer (easiest), GNS3, or EVE-NG. The first lesson helps you pick one and covers IOS basics. Subnetting knowledge helps — see the Subnetting course.
Lab Setup & IOS Basics
You need gear to practice, and a simulator is free. Set up Packet Tracer or GNS3, then learn the IOS command modes every later lesson assumes.
VLANs & Trunking
A VLAN splits one physical switch into many logical networks. Create VLANs, assign access ports, and carry multiple VLANs between switches over a trunk.
Inter-VLAN Routing
VLANs isolate traffic by design — so how do they talk? Route between them with a router-on-a-stick or, better, a Layer 3 switch using SVIs.
Spanning Tree & EtherChannel
Redundant switch links cause catastrophic loops. Spanning Tree blocks loops automatically; EtherChannel bonds links into one for bandwidth without a loop.
Static Routing, Default Routes & HSRP
A router only knows its directly connected networks. Static routes tell it about the rest, a default route handles "everything else," and HSRP gives hosts a redundant gateway.
OSPF
Static routes don’t scale. OSPF is the workhorse interior routing protocol — routers discover each other, share a map of the network, and compute the best paths automatically.
BGP
BGP is the routing protocol of the internet. Where OSPF routes inside an organization, BGP exchanges routes between them — between autonomous systems.
ACLs & NAT
Filter traffic with Access Control Lists and translate private addresses with NAT — two configs you’ll write on almost every router and firewall.