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Key points
- Distributed entryAnycast attracts users to several PoPs through BGP decisions.
- Not a magic filterIt spreads traffic but does not identify attacks by itself.
- Clean delivery mattersAfter mitigation, the path back to the customer must remain stable.
Defining the problem
Anycast announces the same prefix from multiple locations. BGP chooses paths based on routing policy, not a perfect geographic distance calculation. Two nearby users may reach different PoPs depending on their providers.
During a DDoS, this spreads volumetric pressure across several entry points. The trap is believing distribution is enough. If each PoP lacks capacity, if filters are generic or if origin delivery is weak, the attack is only moved.
Anycast also changes troubleshooting. A user may reach one PoP while the monitoring system tests another. Without per-PoP telemetry, support teams can misread a local routing issue as a global outage or miss an attack concentrated on one region.
Why this matters
Anycast matters because it changes the absorption surface. Instead of one port or one scrubbing center, several sites can absorb part of the load and reduce the risk of a single localized failure.
But user experience still depends on latency, asymmetry and route stability. A poor anycast design can move sessions between PoPs, create long return paths or make the clean handoff the real bottleneck.
For DDoS, the relevant capacity is not only total advertised capacity. It is the capacity available at the PoP that actually receives traffic, the quality of upstreams around it and the ability to move or dampen routes without causing instability.
Possible solutions
Protected unicast announces the prefix from one mitigation location and returns clean traffic through tunnel or cross-connect. It is simple and often enough for regional customers.
Full anycast announces the same prefix from several PoPs, with local mitigation and controlled BGP policy. It fits distributed services and truly international users.
A hybrid model uses anycast for entry and a delivery model adapted to the origin. It avoids forcing every service into the same global story.
Some networks use selective announcements: a prefix is anycasted only in regions where capacity and clean delivery are mature. This is often safer than a large map with weak operational control.
- Protected unicast
- Simple and readable for regional needs.
- Global anycast
- Spreads volume but requires capacity and policy.
- Hybrid design
- Distributed entry with clean origin delivery.
| Model | Advantage | Limit |
|---|---|---|
| Protected unicast | Very readable | Less distributed |
| Anycast | Distributes entry | Requires strong PoPs |
| Hybrid | Customer-specific | Needs more design |
Concrete use case
A European SaaS API used in France, Germany and Spain can benefit from anycast if the application itself is distributed. Entries are closer and attacks are spread.
A single-datacenter FiveM server may instead need protected unicast with predictable delivery from Marseille. Global anycast can be less useful if it makes the path less stable.
A DNS or API edge can often tolerate anycast better than a single game session because requests are short and retryable. Persistent UDP or TCP sessions need more caution.
Frequent mistakes
Most mistakes come from marketing-driven anycast. A map with many glowing points does not prove better protection.
A final mistake is ignoring withdrawal behavior. During an incident, removing a PoP announcement can protect users, but only if the remaining sites have enough capacity and the route change does not flap repeatedly.
- Assuming anycast filters bad traffic automatically.
- Ignoring capacity and policy per PoP.
- Forgetting clean delivery to the origin.
- Forcing real-time services into unstable global paths.
- Not testing paths from major customer ISPs.
FAQ
Does anycast always reduce latency?
No. BGP does not always select the geographically shortest path.
Is anycast enough against DDoS?
No. It helps absorb and spread traffic, but filtering and clean delivery remain essential.
Is it good for game servers?
Sometimes, but session stability and return path often matter more.
Can anycast work with tunnels?
Yes, if the entry, scrubbing and delivery model are clearly defined.
