OSPF Packet Tracer Lab

1. Network Diagram Overview

This lab configures OSPF (Open Shortest Path First) on a network consisting of four routers (R1, R2, R3, R4), one switch (SW1), and a PC (PC1). The goal is to ensure routing via OSPF, advertise a default route using an ASBR (Autonomous System Boundary Router), and configure loopback interfaces.

Objectives:

1. Configure the appropriate hostnames and IP addresses on each device. Enable router interfaces. (You don't have to configure ISPR1)

2. Configure a loopback interface on each router (1.1.1.1/32 for R1, 2.2.2.2/32 for R2, etc.)

3. Enable OSPF directly on each interface of the routers. Configure passive interfaces as appropriate.

4. Configure the reference bandwidth on each router so a FastEthernet interface has a cost of 100.

5. Configure R1 as an ASBR that advertises a default route in to the OSPF domain.

6. Check the routing tables of R4. What default route(s) were added? (watch the video for a brief explanation)

7. Use Simulation mode to view the OSPF Hello messages being sent by the routers. What fields are included in the Hello message?

2. Addressing Scheme

Device	Interface	IP Address	Subnet Mask	Description
R1	G0/0	10.0.12.1	255.255.255.252	Link to R2
R1	F1/0	10.0.13.1	255.255.255.252	Link to R3
R1	Loopback0	1.1.1.1	255.255.255.255	Loopback
R2	G0/0	10.0.12.2	255.255.255.252	Link to R1
R2	F1/0	10.0.24.1	255.255.255.252	Link to R4
R2	Loopback0	2.2.2.2	255.255.255.255	Loopback
R3	F1/0	10.0.13.2	255.255.255.252	Link to R1
R3	F2/0	10.0.34.1	255.255.255.252	Link to R4
R3	Loopback0	3.3.3.3	255.255.255.255	Loopback
R4	F1/0	10.0.24.2	255.255.255.252	Link to R2
R4	F2/0	10.0.34.2	255.255.255.252	Link to R3
R4	G0/0	192.168.4.254	255.255.255.0	Link to PC1
R4	Loopback0	4.4.4.4	255.255.255.255	Loopback
PC1	NIC	192.168.4.1	255.255.255.0

3. Step-by-Step Configuration

a. Hostname and Interface Configuration

Each router and switch must be configured with appropriate hostnames and IP addresses.

R1:

Router(config)# hostname R1
R1(config)# interface G0/0
R1(config-if)# ip address 10.0.12.1 255.255.255.252
R1(config-if)# no shutdown
R1(config)# interface F1/0
R1(config-if)# ip address 10.0.13.1 255.255.255.252
R1(config-if)# no shutdown

R2:

Router(config)# hostname R2
R2(config)# interface G0/0
R2(config-if)# ip address 10.0.12.2 255.255.255.252
R2(config-if)# no shutdown
R2(config)# interface F1/0
R2(config-if)# ip address 10.0.24.1 255.255.255.252
R2(config-if)# no shutdown

... Similar commands will be applied to R3, R4, and SW1.

b. Loopback Interface Configuration

Configure a loopback interface on each router for routing purposes.

R1:

R1(config)# interface loopback0
R1(config-if)# ip address 1.1.1.1 255.255.255.255

Repeat similar configurations for R2, R3, and R4, assigning 2.2.2.2/32, 3.3.3.3/32, and 4.4.4.4/32 respectively.

c. OSPF Configuration

Enable OSPF routing directly on each interface and configure passive interfaces where needed.

R1:

R1(config)# router ospf 1
R1(config-router)# network 10.0.12.0 0.0.0.3 area 0
R1(config-router)# network 10.0.13.0 0.0.0.3 area 0
R1(config-router)# network 1.1.1.1 0.0.0.0 area 0
R1(config-router)# passive-interface default
R1(config-router)# no passive-interface G0/0
R1(config-router)# no passive-interface F1/0

Repeat OSPF configuration for R2, R3, and R4, ensuring to include the correct network addresses for each router's interfaces.

d. Reference Bandwidth

Configure the reference bandwidth to adjust OSPF cost calculations, ensuring FastEthernet interfaces have a cost of 100.

R1(config)# router ospf 1
R1(config-router)# auto-cost reference-bandwidth 10000

Apply this configuration to all routers (R1, R2, R3, and R4).

e. ASBR Configuration on R1

R1 will be configured as an ASBR to advertise a default route into the OSPF domain.

R1(config)# ip route 0.0.0.0 0.0.0.0 G0/0
R1(config)# router ospf 1
R1(config-router)# default-information originate

f. Routing Table Verification (R4)

Check the routing table on R4 to see if the default route has been propagated by R1.

R4# show ip route

You should see the default route (0.0.0.0/0) in the routing table, which was learned from R1.

g. OSPF Hello Messages in Simulation Mode

To view OSPF Hello messages, switch to Simulation mode in Packet Tracer and inspect the packets exchanged between the routers.

Fields included in the Hello messages:

• Router ID
• Hello and Dead Intervals
• Neighbors
• Area ID
• Authentication Type (if configured)
• Network Mask

4. Conclusion

By following this guide, you will have configured OSPF on the network, enabling dynamic routing between all routers. R1 is configured as an ASBR, advertising a default route. The reference bandwidth is configured to adjust OSPF cost metrics for FastEthernet links, and OSPF Hello messages are observable in Simulation mode.

Acknowledgements

Special thanks to Jeremy's IT Lab for providing valuable resources and tutorials that greatly contributed to the completion of this exercise. His in-depth explanations and practical demonstrations have been instrumental in enhancing my understanding of Cisco networking concepts and the effective use of Packet Tracer.

For more information and additional resources, visit Jeremy's IT Lab and check out his YouTube for the full course, Jeremy's IT Lab Free CCNA 200-301 | Complete Course