DHCPLB: An open source load balancer

This post introduces DHCPLB, an open-source load balancer designed to address traffic imbalance issues in Facebook's DHCP infrastructure. It details the problem of uneven DHCP request distribution caused by network topology and ECMP limitations, leading to incidents where servers were flooded. DHCPLB was developed to sit behind anycast VIPs and distribute DHCPv4 and DHCPv6 requests among KEA servers. Key features include DHCPv6 support (RFC3315), A/B testing capabilities for KEA server versions, MAC address-based overrides for debugging, integration with Scuba for monitoring, hot-reloading of configuration files, BGP advertisement via ExaBGP, and two balancing algorithms (Round Robin and ModuloN based on Transaction ID). The post also outlines the production rollout and architecture, including TOR relay configuration and DHCPLB deployment.