Sunday, April 27, 2008

Load Balancing with CEF - Cisco Systems

Load Balancing with CEF - Cisco Systems
Load balancing with Cisco Express Forwarding
The use of parallel T1 or E1 links provides higher aggregate bandwidth connections between routers where an upgrade to a high bandwidth DS3 or E3 link is not feasible due to cost, usage patterns or availability. It is also an approach that scales well as links can be added as the bandwidth requirements grow. In IOS software release 11.1(17)CC a new forwarding mechanism called Cisco Express Forwarding (CEF) has been introduced for Cisco 7200 and 7500 series routers. CEF can efficiently use multiple parallel links without additional hardware multiplexers. The purpose of this document is to describe how CEF to uses parallel links and how to configure it. For a more general description of techniques to increase bandwidth with parallel links please see the White Paper "Alternatives for high bandwidth connections using parallel T1/E1 links."
Load balancing
The term Load balancing describes a functionality in a router that distributes packets across multiple links based on layer 3 routing information. If a router discovers multiple paths to a destination the routing table is updated with multiple entries for that destination.

  1. Load balancing with CEF for IP
  2. How CEF load balancing works
  3. Forwarding Information Base
  4. Adjacency Tables
  5. CEF Configuration

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