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Most Common BGP Communities

If you're interested in networking, then you've probably heard of the term "BGP community." But what are they? And what do they do?

In this blog post, we'll take a look at some of the most well-known BGP communities. We'll also discuss their functions and how they can be useful.

So if you're curious about BGP communities and want to learn more, keep reading!


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What is BGP Community?

BGP community is a BGP attribute that can be attached to a route to provide additional information and allow for more granular control in BGP routing decisions. BGP community values are optional and transitive, meaning they can be passed along from one BGP speaker to the next.

This allows for increased flexibility and customizability in BGP routing policies. BGP communities can also be used for hierarchical or organizational purposes, such as identifying routes belonging to a particular service provider or network segment.

What is the Purpose of a BGP Community?

The Border Gateway Protocol (BGP) is a fundamental component of the internet. It is responsible for routing traffic across networks and determining the most efficient path for data to travel. However, BGP was not originally designed to support complex network configurations, leading to issues such as suboptimal routing decisions and security vulnerabilities. This is where BGP communities come in.

A BGP community is a group of network nodes that share a common policy, allowing for better control and management of traffic on the Internet. This can include setting preferred paths for certain types of traffic, controlling the advertisement of routes to certain nodes, and defining actions to take if certain conditions are met.

BGP communities offer increased flexibility and customization for network routing policies. By assigning a community tag to an advertisement, network providers can apply custom configurations for specific types of traffic. This allows for more granular control over traffic flow and optimization based on factors like customer contracts or service level agreements. BGP communities also allow for the application of policies across multiple networks, allowing providers to easily coordinate and manage their routing strategies.

In addition, BGP communities can be used to enhance security by limiting the dissemination of sensitive information to specific nodes or groups. This helps to enhance security by limiting access to this sensitive information and preventing it from being inadvertently leaked outside of the assigned community.

Most Well-Known BGP Communities

When it comes to Border Gateway Protocol (BGP), communities are sets of route attributes that can be used for various purposes, such as routing and traffic engineering. The most commonly known BGP communities include No Export, No Advertise, and Graceful Shutdown. These communities provide highly valuable functions in networking and allow for more efficient routing decisions.

1. No Export

In the BGP routing protocol, a No Export community is used to prevent an announcement from being exported to any external BGP peers. This ensures that traffic intended for the local autonomous system stays within that system and does not get accidentally propagated outside of it. The No Export community can be applied both inbound and outbound on BGP announcements, allowing for fine-tuned control over which routes are shared with external peers. This can also be useful in troubleshooting routing issues or maintaining network security.

2. No Advertise

The No Advertise BGP community is a configuration option for Border Gateway Protocol (BGP) that tells a BGP speaker not to advertise a particular route to its neighbors. This feature can be useful in preventing certain routes from propagating to external networks while still allowing them to be used locally. It can also be helpful in troubleshooting network issues or controlling traffic flow. The No Advertise community is just one of many optional BGP attributes that can be used to fine tune network routing.

3. Graceful Shutdown

The Graceful Shutdown BGP community is used to control the behavior of a router during BGP session shutdown. When applied, it allows for the orderly withdrawal of routes and graceful closure of BGP peering sessions. This helps to minimize network disruption and ensure that all necessary updates are properly propagated in the network. The Graceful Shutdown community can be applied to a specific peer or globally, allowing for fine-tuned control over how the shutdown is handled. This can be a useful tool for facilitating network maintenance or making changes to routing configurations.

Final Words

The BGP community is a powerful tool to manage routing in your network. Using them lets you control how prefixes are handled and which routes are accepted or rejected. This allows for more fine-tuned traffic management and can help improve performance and stability. We encourage you to try them if you’re not already using BGP communities.

They may just be the tool you need to run your network like a well-oiled machine.

Have you ever used BGP communities in your network? What tips do you have for others who want to start using them?

You can learn about lots of BGP Communities in our CCIE Enterprise Infrastructure course.

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.

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