Table of Contents

BGP Multihoming: Plan B for Networks

Network administrators rely on Border Gateway Protocol (BGP) to provide reliable routing between networks. However, if one of your network's gateway routers fails, your organization's networks could be isolated from the rest of the world. Multihoming allows you to configure multiple gateways for your networks, providing a backup in case one of your gateways fails. In this article, we'll discuss how BGP multihoming works and how you can set it up in your own organization.

What Is BGP Multihoming?

BGP multihoming is a practice in network routing that involves connecting a single network to multiple ISPs, increasing the stability and redundancy of the network's external connections. In the event that one ISP experiences a connection issue or outage, multihomed BGP ensures that traffic can still flow through the other connected ISPs. This allows for more reliable internet service and can also provide greater bandwidth capacity. While BGP multihoming does have some cost and configuration considerations, it can significantly improve the overall performance and resiliency of a network.

How Does BGP Multihoming Work?

As it is said before, BGP Multihoming is a networking technique used to improve the reliability and availability of internet connections. It works by connecting a single organization or network to multiple ISPs, creating redundant pathways for data to travel through. This not only offers increased uptime in case one ISP experiences a failure, but it can also improve overall network performance.

In order to properly accomplish BGP Multihoming, an organization must establish separate BGP sessions with each ISP and configure their own autonomous system number (ASN). After the organization configures its ASN, the organization's routers will then advertise their ASN and appropriate routes to each ISP, allowing them to route traffic efficiently through the most reliable connection at any given moment.

Prerequisites of BGP Multihoming

When it comes to BGP multihoming, several prerequisites must be met to establish a reliable and stable network. Let's talk about some prerequisites of BGP multihoming:

Autonomous System Number

To establish multihoming, a network must first have an Autonomous System Number (ASN). This unique number is assigned by ARIN or another organization and is used to identify a specific autonomous system, typically associated with a single organization or network provider. Without an ASN, BGP multihoming cannot be properly established, as there would be no way to distinguish the autonomous system from others.

Furthermore, without an ASN, the autonomous system would not be able to exchange routing information with other autonomous systems through BGP. In short, it is crucial for a network to obtain an ASN before attempting to set up BGP multihoming.

IP-Addressing and Routing

Without a provider-independent addressing and routing setup, a network would not have control over its own unique IP address space and routes and would instead be dependent on a single provider for these services. By ensuring provider independence in these areas, a network can successfully implement BGP multihoming and reap the benefits of increased connectivity and resiliency.

Router Hardware

When it comes to multihoming, having the proper router hardware is crucial. A minimum of 128 MB of RAM is required for BGP, but it's recommended to have at least 256 MB to support more routes and peers. Additionally, it's important to have enough CPU power to handle the increased routing traffic and processing. It's also worth considering factors such as flash memory capacity for storing routing information, interfaces for connecting to multiple ISPs, and future expansion options. By investing in the right router hardware before implementing BGP multihoming, organizations can ensure they have the necessary resources to effectively handle their network traffic.

Final Words

BGP multihoming is a powerful tool that can help your network maintain uptime and stability in the event of an outage or unexpected failure. Using multiple connections to different providers creates a backup plan that will keep your business up and running even when one provider fails. If you’re interested in learning more about BGP multihoming or implementing it into your own network, be sure to check out our website for additional resources. We are more than happy to help you.

Created by
Stanley Avery

I am a certified network engineer with over 10 years of experience in the field. I have a deep understanding of networking and IT security, and I am always looking for new challenges.

View profile