🛰️ Multi-Area OSPF Lab – Design Overview

 

🛰️ Multi-Area OSPF Lab – Design Overview

🎯 Goal:

Build a multi-area OSPF network with 4 routers and 4 PCs, where:

  • Each router has its own LAN.

  • Routers belong to different OSPF areas.

  • All networks communicate through Area 0 (the backbone area).

🖥️ Network Topology

PC1 -- R1 -- R2 -- R3 -- R4 -- PC4
         |         |
        PC2       PC3

Area Design

OSPF AreaRouter(s)Description
Area 0R2–R3Backbone area
Area 1R1Connected to Area 0 via R2
Area 2R4Connected to Area 0 via R3

IP Address Plan

RouterInterfaceIP AddressNetworkOSPF Area
R1G0/0192.168.1.1192.168.1.0/24Area 1
S0/0/010.0.0.110.0.0.0/30Area 1
R2S0/0/010.0.0.210.0.0.0/30Area 1
S0/0/110.0.0.510.0.0.4/30Area 0
G0/0192.168.2.1192.168.2.0/24Area 0
R3S0/0/110.0.0.610.0.0.4/30Area 0
S0/0/010.0.0.910.0.0.8/30Area 2
G0/0192.168.3.1192.168.3.0/24Area 0
R4S0/0/010.0.0.1010.0.0.8/30Area 2
G0/0192.168.4.1192.168.4.0/24Area 2

Each PC will have an IP in its router’s LAN network:

  • PC1: 192.168.1.10

  • PC2: 192.168.2.10

  • PC3: 192.168.3.10

  • PC4: 192.168.4.10

🪜 Configuration Steps (Router Commands)

🔹 R1 (Area 1)

enable
conf t
interface g0/0
 ip address 192.168.1.1 255.255.255.0
 no shutdown
exit
interface s0/0/0
 ip address 10.0.0.1 255.255.255.252
 clock rate 64000
 no shutdown
exit
router ospf 1
 network 192.168.1.0 0.0.0.255 area 1
 network 10.0.0.0 0.0.0.3 area 1

🔹 R2 (ABR: connects Area 1 & Area 0)

enable
conf t
interface s0/0/0
 ip address 10.0.0.2 255.255.255.252
 no shutdown
exit
interface s0/0/1
 ip address 10.0.0.5 255.255.255.252
 clock rate 64000
 no shutdown
exit
interface g0/0
 ip address 192.168.2.1 255.255.255.0
 no shutdown
exit
router ospf 1
 network 10.0.0.0 0.0.0.3 area 1
 network 10.0.0.4 0.0.0.3 area 0
 network 192.168.2.0 0.0.0.255 area 0

🔹 R3 (ABR: connects Area 0 & Area 2)

enable
conf t
interface s0/0/1
 ip address 10.0.0.6 255.255.255.252
 no shutdown
exit
interface s0/0/0
 ip address 10.0.0.9 255.255.255.252
 clock rate 64000
 no shutdown
exit
interface g0/0
 ip address 192.168.3.1 255.255.255.0
 no shutdown
exit
router ospf 1
 network 10.0.0.4 0.0.0.3 area 0
 network 10.0.0.8 0.0.0.3 area 2
 network 192.168.3.0 0.0.0.255 area 0

🔹 R4 (Area 2)

enable
conf t
interface s0/0/0
 ip address 10.0.0.10 255.255.255.252
 no shutdown
exit
interface g0/0
 ip address 192.168.4.1 255.255.255.0
 no shutdown
exit
router ospf 1
 network 192.168.4.0 0.0.0.255 area 2
 network 10.0.0.8 0.0.0.3 area 2

🧾 Verification Commands

show ip ospf neighbor
show ip route ospf
show ip ospf interface
show ip protocols

✅ You should see OSPF neighbors formed across routers and routes marked with O in routing tables.

🧠 What Students Learn

ConceptDescription
Multi-area OSPFDivides network into multiple areas for scalability
ABR (Area Border Router)Connects different OSPF areas
Backbone Area (0)Central area all others must connect to
OSPF MetricCost based on bandwidth
BenefitReduces routing overhead and improves efficiency

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