Core Issue
Organizations use parallel links to make higher bandwidth available to network users. The network's traffic is load balanced over these multiple links. This is a scalable, cost effective way of providing aggregate bandwidth greater than that available with a single link.
Cisco Express Forwarding (CEF) is a Layer 3 (L3) IP switching technology. Compared to other switching technologies, CEF provides superior performance, especially in networks with dynamic traffic patterns. With CEF switching enabled, load balancing over parallel links is possible. CEF supports both per-destination and per-packet load balancing. Additionally, CEF supports per-packet load balancing without performance degradation. This is a major advantage over certain switching mechanisms like fast switching, where route-caching needs to be disabled for per-packet load balancing to work.
Resolution
By default, CEF load balances on a per-destination basis. To enable per-packet load balancing on a CEF interface, issue the ip load-sharing command with the per-packet keyword in interface configuration mode.
For more information on configuring and verifying load balancing with CEF, refer to Load Balancing with CEF.
