Routers are the backbone of any computer network.
They decide where each packet should go — whether it’s heading to a local network or needs to be forwarded to another router to reach its destination.

In this hands-on Cisco Packet Tracer project, I explored how routers perform packet forwarding and next-hop routing based on their routing tables.
By the end, you’ll see how routers make smart decisions to deliver packets across multiple networks efficiently.

🔧 Project Overview

🎯 Objective:
To understand how routers forward packets and use next-hop routing to reach networks they are not directly connected to.

🧱 Tools Used:

• Cisco Packet Tracer

• Two routers (R0 and R1)

• Two PCs (PC0 and PC1)

• Copper Cross-over cables

⚙️ Step-by-Step Configuration

🖥️ Step 1: Network Topology Setup

We’ll create the following topology:

PC0 ---- R0 ---- R1 ---- PC1

IP Addressing Scheme:

🧩 Step 2: Configure Router R1

enable
configure terminal
interface gigabitEthernet0/0
 ip address 192.168.10.1 255.255.255.0
 no shutdown
exit
interface gigabitEthernet0/2
 ip address 10.0.0.1 255.0.0.0
 no shutdown
exit
end

Verify:

show ip interface brief

Expected:

GigabitEthernet0/0     192.168.10.1     up     up
GigabitEthernet0/2     10.0.0.1         up     up

🔌 Step 3: Configure Router R2

enable
configure terminal
interface gigabitEthernet0/0
 ip address 10.0.0.2 255.0.0.0
 no shutdown
exit
interface gigabitEthernet0/2
 ip address 172.16.5.1 255.255.255.0
 no shutdown
exit
end

Verify:

show ip interface brief

💻 Step 4: Configure PCs

PC1

IP Address: 192.168.10.2
Subnet Mask: 255.255.255.0
Default Gateway: 192.168.10.1

PC2

IP Address: 172.16.5.2
Subnet Mask: 255.255.255.0
Default Gateway: 172.16.5.1

🛰️ Step 5: Test Direct Connections

• From PC0:
  ping 192.168.10.1 ✅

• From R0:
  ping 10.0.0.2 ✅

• From PC1:
  ping 172.16.5.1 ✅

📡 Step 6: Configure Static Routes

Since R0 and R1 are connected via the 10.0.0.0/8 network, each must be told about the other’s connected networks.

On R0:

ip route 172.16.5.0 255.255.255.0 10.0.0.2

On R1:

ip route 192.168.10.0 255.255.255.0 10.0.0.1

🧪 Step 7: End-to-End Testing

Now try from PC0:

ping 172.16.5.2

Output:

Reply from 172.16.5.2: bytes=32 time<1ms TTL=126
Reply from 172.16.5.2: bytes=32 time<1ms TTL=126
Reply from 172.16.5.2: bytes=32 time<1ms TTL=126
Reply from 172.16.5.2: bytes=32 time<1ms TTL=126

✅ All packets were successfully delivered with no timeouts.
This confirms that the routing configuration was perfect and both routers forwarded packets flawlessly between the two networks.

🧭 How Packet Forwarding Works (Step-by-Step)

1. PC0 sends a packet to 172.16.5.2.
   It checks the destination and sees it’s not in the same subnet, so it forwards it to its default gateway (R1).

2. R0 checks its routing table.
   It finds no direct match for 172.16.5.0/24, but the static route tells it:
   “To reach 172.16.5.0/24, send it to next-hop 10.0.0.2.”

3. R0 forwards the packet to R1 using the IP 10.0.0.2.

4. R1 receives it, sees the destination is 172.16.5.2, which belongs to its directly connected network, and sends it to PC1.

5. PC1 replies to the source (PC0) using its own default gateway (R1), and the same route works in reverse.

⚡ Output Verification

• show ip route on both routers displays static routes.

• show ip arp confirms MAC address resolution.

• Packet Tracer Simulation mode shows ARP and ICMP steps visually.

💡 Key Learnings

• Routers forward packets based on destination IP and routing table entries.

• When a network is not directly connected, routers use next-hop IP addresses to reach it.

• Static routes manually define the path to remote networks.

🚀 Conclusion

This project was a great way to visualize how routers think!
By configuring two routers and setting up static routes, I learned how packet forwarding and next-hop routing form the foundation of real-world networking.

From ARP resolution to routing decisions, this simulation clarified how every IP packet finds its way home.

🧩 Repository

🔗 Project Repository: https://github.com/Aadi0729/Packet-Forwarding-Routing

🎥 Watch Simulation: https://drive.google.com/file/d/18E-6MjF7-ZQn6EH25-dOiGdX2_LDhK_f/view?usp=drive_link