What algorithms do load balancers use for traffic distribution?

Load balancing algorithms: Round Robin (equal rotation), Weighted Round Robin (proportional to capacity), Least Connections (to server with fewest active connections), Weighted Least Connections (considers weights), IP Hash (consistent server per client IP - session persistence), Least Response Time (to fastest server), Random. Layer 4 (TCP) load balancers route by IP/port; Layer 7 (HTTP) can route by URL, headers, cookies. Consider health checks, session persistence, geographic routing.