Cloud routing is not just packet forwarding – it is a critical component that determines whether your application will be available everywhere at any time. In Amazon Web Services (AWS) one of the most important mechanisms ensuring stable and fast access is the BGP (Border Gateway Protocol). In this article we will look at how BGP works in Amazon Web Services, its role in AWS Direct Connect BGP configuration, and how it influences application performance in AWS and high availability.
What is BGP and why is it important in the cloud?
BGP is a protocol for exchanging routing information between autonomous systems (AS). In traditional carrier networks it selects the shortest path between two networks. In AWS cloud it serves a similar purpose but with an extra dimension: it must cooperate with dynamically scaling resources and ensure service continuity even when one connection fails.
The main advantage of BGP is the ability to dynamically adjust routes in response to topology changes. When a connection becomes unavailable, BGP automatically selects an alternate path, minimizing downtime. This is why BGP and high availability in the cloud becomes a practical solution.
How does BGP work in Amazon Web Services?
In AWS BGP is used in several scenarios: in the Amazon VPC service when connecting to on‑premise via AWS Direct Connect, when using Transit Gateway, and in VPN CloudHub. Each of these connections has its own AS number, and AWS provides its own AS number (e.g., 7224) or allows you to use your own if you have one.
During BGP session establishment, both ends exchange information about available IP prefixes. AWS advertises VPC prefixes, and the customer advertises their own (e.g., corporate network). This enables traffic to flow smoothly between environments, and BGP chooses the most cost‑effective and low‑latency route.
AWS Direct Connect BGP configuration – step by step
- Create a private
Virtual Interfaceand assign your own AS number. - Configure the BGP session on the on‑premise router, providing IP addresses on both sides and the AWS AS number.
- Define the prefix ranges to be advertised – typically the entire VPC network and any additional subnets.
- Set the
hold timeandkeepalive intervalaccording to AWS recommendations (usually 30 s and 10 s). - Monitor the BGP session with CloudWatch or your own SNMP tools to quickly detect any interruptions.
A proper configuration ensures that the impact of BGP on application performance in AWS is minimal – latency is limited to a few milliseconds, and throughput depends solely on the chosen Direct Connect plan.
Impact of BGP on application performance in AWS
In practice BGP does not directly increase bandwidth, but it influences the quality of the connection. Properly setting local preference and MED attributes allows you to control which link is preferred – for example, favoring Direct Connect over public Internet.
In a failure scenario where Direct Connect is cut off, BGP automatically shifts traffic to a VPN tunnel. This keeps applications available, with only a brief increase in latency.
“BGP is not just a protocol – it is a mechanism that lets the cloud maintain continuity even when the physical layer is disrupted.”
Common mistakes and trade‑offs when using BGP in AWS
- Incorrect AS number – using the same AS number on both sides causes a conflict and the session will not be established.
- Overly broad advertised prefixes – publishing the entire corporate network can unnecessarily load the routing table.
- Lack of monitoring – without alerts on BGP session loss, failures may go unnoticed for a long time.
- Hold time settings – too long a time can delay failure detection, too short can cause unnecessary flaps.
A comprehensive approach requires balancing reaction speed with session stability. In many cases it is worth implementing BGP redundancy – two independent Direct Connect sessions in different regions.
Practical checklist – BGP in AWS ready for deployment
- Verify the AS number – are you using your own or AWS's?
- Check IP addresses on both sides – are they in the same /30 subnet?
- Define the prefixes to be advertised – limit them to the necessary ranges.
- Configure
hold timeandkeepalive intervalaccording to guidelines. - Enable BGP session monitoring in CloudWatch and set alarms for
BGPState = down. - Test failover – disable Direct Connect and verify traffic switches to VPN.
Following these steps provides a stable and high‑performance infrastructure where BGP routing in the cloud acts as an invisible guardian of availability.
Conclusion – why you should care about BGP in AWS
Through a thoughtful AWS Direct Connect BGP configuration you gain not only better application performance but also a solid foundation for building highly available solutions. BGP automatically reacts to network changes, minimizing downtime and ensuring seamless access to resources.
If you want your cloud applications to leverage the full potential of BGP, contact us at Coderia.it – we will help design and implement an optimal network architecture tailored to your needs.
