🛰️ OSPF Routing Lab

Overview

This lab demonstrates a full OSPF routing environment consisting of multiple OSPF areas connected through ABRs. The objective is to show:

• OSPF Area design (Standard & NSSA)
• Inter-area communication
• Default route propagation
• NAT configuration for internet access
• PAT (Port Address Translation) implementation
• Virtual Link usage
• End-to-End connectivity test

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🔧 Technologies Used

• Cisco IOS Routers (GNS3 or Packet Tracer)
• OSPF Protocol (Single AS)
• NAT/PAT
• ACL (Optional)
• IP Routing (Static & Dynamic)

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📡 Topology Description

The topology contains:

• 9 OSPF Areas:

  • Area 0 (Backbone)
  • Area 20, 22, 23, 30, 31, 32, 40, 45 (Standard / NSSA)

• Routers:

  • Core routers acting as ABRs and redistribution points
  • Edge routers managing NAT, PAT, and WAN access
  • All routers run the Cisco IOS image: c7200-adventerprisek9-mz.124-24.T5

• Servers:

  • Distributed in each area to test reachability and simulate services
  • Implemented using regular PCs in GNS3 to simulate servers
  • Verified with successful ping tests to ensure full connectivity

• Internet (via R-WAN):

  • Connected through R-WAN router
  • Used to verify default route propagation and PAT configuration

• Switch:

  • Switch1 is used to aggregate devices in Area 45

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🌐 Key Configurations

OSPF Configuration Example

router ospf 1
 router-id 1.1.1.1
 network 10.1.0.0 0.0.0.255 area 0

Default Route Injection

ip route 0.0.0.0 0.0.0.0 <next-hop/interface>
router ospf 1
 default-information originate

NAT & PAT Example

interface Gig0/1
 ip nat outside
interface Gig0/0
 ip nat inside
ip nat inside source list 1 interface Gig0/1 overload
access-list 1 permit 10.0.0.0 0.255.255.255

Virtual Link Example

! Router R1 - Router ID: 1.1.1.1
router ospf 1
 router-id 1.1.1.1
 area 20 virtual-link 2.2.2.2

! Router R2 - Router ID: 2.2.2.2
router ospf 1
 router-id 2.2.2.2
 area 20 virtual-link 1.1.1.1

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✅ Testing

Ping Test Example 1

Ping Test Example 2

Traceroute Test Example

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🧠 What You Learn

• OSPF area types and summarization

• Virtual link use cases and configuration

• Inter-area route propagation

• NAT/PAT behavior and configuration

• Best practices for default route injection and Internet access

• Layer 3 design with OSPF in multi-area environments

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📌 Notes

• Each router has a dedicated Loopback interface used as the Router ID.

  • This ensures stable OSPF operations and consistent identification of routers across the topology.

• A virtual link is required when an area (like Area 22) is not directly connected to Area 0.

• Verify WAN reachability using ping and traceroute.

• Make sure to propagate the default route into non-backbone areas.

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📂 Files To Include

• topology.png – full topology
• ping1.png – successful ping test 1
• ping2.png – successful ping test 2
• trace.png – successful trace test
• Configurations – All router configuration files
• OSPF Lab GNS3 – Project file for GNS3
• Router Image – Cisco IOS image used in lab

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🔗 Author

LinkedIn: Mohamed Sami GitHub: Mohamed Sami

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🔑 Keywords

OSPF, Cisco, Routing Lab, GNS3, Cisco Packet Tracer, Virtual Link, Multi-area OSPF, OSPF NSSA, OSPF Areas, Router ID, PAT, NAT, Cisco IOS, CCNA, CCNP, Network Simulation, Topology Design, GNS3 Project, OSPF Lab, IP Routing