Load balanced traffic over ECMP or LAG in large-scale environments such as core networks or mobile backhauling is a key feature that should be highly optimized to avoid inefficient use of invaluable network resources. With the potential for literally dozens of high-speed links being involved, failing to properly balance traffic can easily lead to link congestion and/or significant underutilization of available capacity.
With this said, unfortunately, the complexities involved with hash selection combined with widely varying traffic patterns and content means that hashing and load balancing is one of those areas where it’s almost impossible to please everyone all the time. The hash that yields near-perfect balance in one network may result in unbalanced traffic on another due to the simple fact that different traffic encapsulations, combined with differing hash capabilities, hashing defaults, and configuration specifics, add up to yield so many permutations.
This chapter explores Junos load balancing (LB) over Trio-based line cards. By better understanding Junos LB behavior and the various options available to modify the result, each user is better able to optimize the behavior to the specifics of their network.
Let’s begin by defining some key terms along with exploring Junos LB defaults and capabilities.
By default, Junos performs per-prefix load balancing, meaning that only the destination address is factored into ...