How to protect a multi-site infrastructure against DDoS attacks

Problem definition

A multi-site infrastructure means several technical locations actively contribute to service delivery. A DDoS attack can therefore do more than target one IP: it can create routing imbalance, saturate shared links, move the problem from one site to another or break clean traffic delivery.

The real issue is not only raw bandwidth. PPS pressure, BGP consistency, asymmetric routing, handoff logic and operational visibility matter just as much. Multi-site Anti-DDoS protection must be designed as a traffic architecture, not just as a packet filter.

Why it matters

Multi-site often looks resilient on paper. In reality, if site roles are unclear or clean traffic return paths are poorly designed, distributed infrastructure becomes harder to defend than a simple one.

This is also a business issue. Customers expect a credible multi-site network to remain reachable, predictable and well-routed during an attack, not to collapse into emergency workarounds.

Possible solutions

There are three main models: centralized mitigation with delivery back to multiple sites, local protection at each site, or a hybrid model mixing shared mitigation with selective local handling.

In many cases, the best answer is not full duplication. It is shared absorption capacity plus flexible clean traffic delivery to the right site.

Our approach

At Peeryx, we start from the traffic path before discussing the filtering engine. We map exposed prefixes, entry points, critical services and return paths first.

The right questions are: where does attacked traffic enter, where is it cleaned, where should clean traffic go back, what happens if one path fails and what must stay simple for operations?

When this makes sense

A multi-site DDoS design is highly relevant when several datacenters, POPs or cloud regions must remain reachable under different latency constraints.

It is less relevant in this exact form if the whole production stack truly lives on one site and there is little routing control or operational maturity.

• Relevant when you run several exposed datacenters or edge locations.
• Relevant when different services must receive clean traffic at different destinations.
• Relevant when you want to share mitigation capacity without rebuilding every site.
• Less relevant if everything truly runs on one site.
• Less relevant if routing control and failover processes do not exist yet.

Real-world example

Imagine a platform split between Marseille, Paris and a European cloud region. Public prefixes are announced through protected IP transit. During an attack, traffic is absorbed and cleaned upstream, then delivered back to Marseille for core services, Paris for segregated administration and the cloud region for selected application components.

The value of multi-site here is not just geographic distribution. It is the ability to send clean traffic to the correct destination based on service function instead of forcing everything through one exit point.

Common mistakes

Most failures come from poor architecture rather than from the filtering engine itself.

• Assuming multi-site automatically means resilience.
• Announcing multiple paths without clear destination logic.
• Forgetting failover for tunnels, ports or return paths.
• Duplicating weak mitigation everywhere instead of sharing what can be shared.
• Underestimating observability and diagnosis time.
• Ignoring latency and asymmetric routing effects.

Comparison table

This quick comparison helps frame the main trade-offs.

Why choose Peeryx

Peeryx focuses on usable protection architecture: protected IP transit, flexible delivery modes, clean traffic handoff and a design mindset suited to serious technical environments.

For multi-site environments, that means building something coherent between mitigation, routing, latency and operations rather than stacking vague promises.

FAQ

Useful resources

These references are useful to extend the architectural and operational side of the topic.