Practical 10

AIM:

To configure routers using the Border Gateway Protocol (BGP) to establish inter-domain routing between different autonomous systems (AS) in a network.

Introduction to BGP:

Border Gateway Protocol (BGP) is a path-vector routing protocol crucial for routing data across different autonomous systems (AS) on the Internet. It enables routing information exchange on a global scale, making it the backbone of the Internet’s routing structure.

Advantages of BGP:

Inter-domain Routing: Essential for routing between different ASes, enabling global Internet connectivity.
Control over Routing Decisions: Allows administrators to implement complex policies, offering fine control over data flow.
Robustness and Stability: BGP is resilient to network changes, ensuring stable routing in dynamic environments.

Disadvantages of BGP:

Complex Configuration: More complicated than IGPs like OSPF and RIP, requiring careful management.
Slow Convergence: BGP may take longer to adapt to network changes, potentially causing temporary routing issues.
Resource Intensive: Requires significant CPU and memory, especially in networks with numerous routes.

Step-by-Step Configuration:

Step 1: Create the Network Topology

Open Cisco Packet Tracer and select the necessary devices.
Arrange devices to form the desired network topology.

Step 2: Configure PCs (Hosts) with IPv4 Addresses

For each PC, go to Desktop > IP Configuration.
Assign the IPv4 address and Subnet Mask as specified in the IP addressing table.
To verify IP settings, use the ipconfig command or configure directly in the command terminal:
```
ipconfig <IPv4 address> <subnet mask> <default gateway>
```

Step 3: Configure Router with IP Address and Subnet Mask

Select Router0, go to Config > Interfaces.
Ensure that all required ports are enabled.
Assign IP addresses to the FastEthernet and Serial ports based on the IP addressing table.

Code: BGP Configuration for Routers

Router 0 Configuration:


Router(config)# router bgp 100
Router(config-router)# network 192.168.1.0
Router(config-router)# network 192.168.2.0
Router(config-router)# neighbor 192.168.2.3 remote-as 200
Router(config-router)# neighbor 192.168.3.2 remote-as 200
Router(config-router)# exit

Router 1 Configuration:


Router(config)# router bgp 200
Router(config-router)# network 192.168.2.0
Router(config-router)# network 192.168.3.0
Router(config-router)# neighbor 192.168.2.2 remote-as 100
Router(config-router)# neighbor 192.168.1.2 remote-as 200
Router(config-router)# exit

Step 4: Assign Routes to Routers

After configuring all devices, assign BGP routes for each router.
For each router, go to CLI, and type the relevant commands to assign routes:
```
network <network id>
```

Summary

This practical demonstrates the configuration of routers using BGP, highlighting how it enables efficient, inter-domain routing on the Internet, providing control over routing policies, and supporting stability in large networks.