Worth Reading: Characterizing IPv6 load balancing

Routers that perform load balancing choose among multiple next-hop routers when forwarding packets. In Figure 1, router R1 chooses among R2 and R3. In general, the next-hop is chosen by computing a hash over a subset of fields in each packet’s IP header. Hashing different subsets of IP header fields allow control of a trade-off between the granularity of load balancing and impact on traffic. Below we describe common load balancing configurations, how well they can load balance traffic, and their possible impact on traffic. —APNIC