OSPF Multi-Router Topology – Cisco Packet Tracer Project

📌 Overview

This project simulates a multi-router OSPF (Open Shortest Path First) network with 4 routers connected via point-to-point links. Each router has its own LAN and participates in the same OSPF process (Process ID 10) in Area 0. The configuration includes OSPF routing, verification steps, ACLs for traffic filtering, and failover testing.

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🖥️ Devices & Topology

• Router0 – LAN: 192.168.1.0/24
• Router1 – LAN: 192.168.20.0/24
• Router2 – LAN: 192.168.30.0/24
• Router3 – LAN: 172.16.0.0/24

🔗 Transit Networks:

• R0 ↔ R2: 10.0.0.0/30
• R0 ↔ R3: 11.0.0.0/30
• R1 ↔ R2: 12.0.0.0/30
• R1 ↔ R3: 13.0.0.0/30

All routers are in OSPF Area 0 and use Process ID 10.

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⚙️ Configuration Summary

OSPF Basic Configuration (Example for Router0):

router ospf 10
 router-id 5.5.5.5
 log-adjacency-changes
 network 192.168.1.0 0.0.0.255 area 0
 network 10.0.0.0 0.0.0.3 area 0
 network 11.0.0.0 0.0.0.3 area 0

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🔍 OSPF Verification Commands

Check OSPF Neighbors:

show ip ospf neighbor

View OSPF Routes:

show ip route ospf

Check OSPF-enabled Interfaces:

show ip ospf interface brief

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🔒 ACL Configuration

To block ICMP (ping) from PC in 192.168.30.0/24 to 172.16.0.0/24, the following ACL is applied on Router2:

Step 1: Create the ACL

access-list 110 deny icmp 192.168.30.0 0.0.0.255 172.16.0.0 0.0.0.255
access-list 110 permit ip any any

Step 2: Apply the ACL

interface GigabitEthernet0/2
ip access-group 110 out

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🔁 OSPF Failover Simulation

To test OSPF failover:

1. Shutdown one transit link (e.g., GigabitEthernet0/0 on Router0):

   interface GigabitEthernet0/0
   shutdown
   

2. Ping from a device in Router0's LAN to a PC in 192.168.30.0.
3. Verify traffic reroutes through the second path using:

   show ip route ospf
   

4. Re-enable the interface:

   no shutdown
   

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✅ Result

• OSPF neighbors form successfully.
• All routers learn remote LANs via OSPF.
• ACL works as expected.
• Network continues to function after link failure (OSPF failover successful).

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🎉 Project Completed Successfully