What are the limitations of using only a Linux firewall for DDoS protection, and when should you consider other solutions?

Linux firewalls are effective for mitigating *some* DDoS attacks, particularly smaller, simpler ones. However, they have limitations: 1) They can be overwhelmed by large-scale volumetric attacks. 2) They require careful configuration and maintenance. 3) They don't protect against application-layer attacks effectively. Consider cloud-based DDoS mitigation services (e.g., Cloudflare, Akamai) or dedicated hardware appliances when facing large-scale attacks, application-layer attacks, or needing high availability.