Multi-Site Enterprise LAN/WAN Design (OSPF)

Author: Michael Chileshe

A 3-site enterprise network built to practice multi-area OSPF, VLAN segmentation, router-on-a-stick inter-VLAN routing, and WAN connectivity. Built in Cisco Packet Tracer and reproduced in GNS3.

Objectives

• Design and implement a 3-site multi-area OSPF network (backbone + 3 LAN areas)
• Segment each site's LAN with VLANs and route between them via router-on-a-stick
• Establish WAN connectivity between HQ and both branches over point-to-point links
• Verify full OSPF adjacency and end-to-end reachability across all sites

Topology

                 HQ-RTR (1.1.1.1)
              VLANs 10/20/30 · Area 10
                 /              \\
     10.0.12.0/30              10.0.13.0/30
       (Area 0)                  (Area 0)
            /                        \\
   BR1-RTR (2.2.2.2)          BR2-RTR (3.3.3.3)
   VLANs 10/20 · Area 20      VLANs 10/20 · Area 30

Site	Router	Switch	Router ID	OSPF Area (LAN)	LAN subnets
HQ	HQ-RTR	HQ-SW1	1.1.1.1	10	10.10.10.0/24, 10.10.20.0/24, 10.10.30.0/24
Branch1	BR1-RTR	BR1-SW1	2.2.2.2	20	10.20.10.0/24, 10.20.20.0/24
Branch2	BR2-RTR	BR2-SW1	3.3.3.3	30	10.30.10.0/24, 10.30.20.0/24

All WAN links and router loopbacks sit in Area 0 (backbone). Each site's router is the ABR for its own LAN area — a standard hub-and-spoke multi-area OSPF design.

Repo structure

multisite-ospf-lab/
├── README.md
├── docs/
│   ├── ip-addressing.md      — full IP/VLAN plan
│   ├── configs/
│   ├── HQ-RTR.txt
│   ├── HQ-SW1.txt
│   ├── BR1-RTR.txt
│   ├── BR1-SW1.txt
│   ├── BR2-RTR.txt
│   └── BR2-SW1.txt
└── topology/
    └── (  topology.pkt )

Deliverables

#	Deliverable	Location
1	Topology diagram	This README (above)
2	IP addressing & VLAN plan	docs/ip-addressing.md
3	Router configs (HQ, Branch1, Branch2)	configs/HQ-RTR.txt, configs/BR1-RTR.txt, configs/BR2-RTR.txt
4	Switch configs (HQ, Branch1, Branch2)	configs/HQ-SW1.txt, configs/BR1-SW1.txt, configs/BR2-SW1.txt
5	Packet Tracer topology file	topology/multisite-ospf-lab.pkt (add after building)
6	Verification evidence (OSPF neighbor/route output, ping tests)	docs/verification.md or screenshots in topology/ (add after testing)

Verification checklist

• All OSPF neighbors show state FULL
• show ip route ospf on each router shows routes to the other two sites' LANs
• End-to-end ping from a Branch1 PC to a Branch2 PC succeeds
• show ip ospf interface brief confirms correct area assignment per interface
• Inter-VLAN routing works within each site (PC in VLAN10 can reach PC in VLAN20 at the same site)