OSPF Open Shortest Path First practical in cisco packet tracer

🌐 OSPF (Open Shortest Path First)

OSPF is a link-state dynamic routing protocol that automatically exchanges routing information between routers and calculates the shortest path using the SPF algorithm.

This is dynamic routing.

Until now in static routing:

👉 You manually added routes.

Now with OSPF:

👉 Routers automatically learn routes from each other.

This is heavily used in:

• Enterprise networks
• ISPs
• Data centers
• Corporate environments

🎯 What You Will Learn

• ✔ Dynamic route learning
• ✔ Neighbor relationships
• ✔ Route advertisement
• ✔ Automatic path selection
• ✔ Scalable routing

🔥 Difference: Static vs OSPF

🧪 Practical Topology

In Cisco Packet Tracer create:

PC0 --- R1 --- R2 --- R3 --- PC1

🌐 IP Addressing Plan

🔹 LAN Networks

🔹 Router-to-Router Links

🔌 Wiring (IMPORTANT)

PC Connections

Router Connections

⚙️ Step 1: Configure Router Interfaces

🔹 Router1

enable
configure terminal

interface g0/0
ip address 10.0.0.1 255.255.255.0
no shutdown

interface g0/1
ip address 192.168.1.1 255.255.255.252
no shutdown

🔹 Router2

enable
configure terminal

interface g0/0
ip address 192.168.1.2 255.255.255.252
no shutdown

interface g0/1
ip address 192.168.2.1 255.255.255.252
no shutdown

🔹 Router3

enable
configure terminal

interface g0/0
ip address 192.168.2.2 255.255.255.252
no shutdown

interface g0/1
ip address 20.0.0.1 255.255.255.0
no shutdown

⚙️ Step 2: Configure PCs

PC0

IP: 10.0.0.10

Gateway: 10.0.0.1

PC1

IP: 20.0.0.10

Gateway: 20.0.0.1

❌ Test Before OSPF

From PC0:

ping 20.0.0.10

❌ Fail

Because routers don’t know remote networks yet.

🔥 Step 3: Configure OSPF

🔹 Router1

router ospf 1

network 10.0.0.0 0.0.0.255 area 0
network 192.168.1.0 0.0.0.3 area 0

🔹 Router2

router ospf 1

network 192.168.1.0 0.0.0.3 area 0
network 192.168.2.0 0.0.0.3 area 0

🔹 Router3

router ospf 1

network 192.168.2.0 0.0.0.3 area 0
network 20.0.0.0 0.0.0.255 area 0

🧠 Important Concept

What is Area 0?

👉 Backbone area of OSPF

All routers communicate inside Area 0.

🔥 Step 4: Verify Neighbor Relationship

Run:

show ip ospf neighbor

You should see neighboring routers.

🔥 Step 5: Verify Routing Table

Run:

show ip route

You’ll see routes marked:

O

👉 Means learned through OSPF

🧪 Final Test

From PC0:

ping 20.0.0.10

✔ SUCCESS

Disclaimer