Specifications

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Cisco MWR 2941 Mobile Wireless Edge Router Release 3.5 Software Configuration Guide, Cisco IOS Release 15.1(3)MR
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Chapter 13 Configuring Cisco Express Forwarding
Configuring Cisco Express Forwarding
Supported Features
Cisco IOS Release 15.0(1)MR supports the following CEF features:
• Per-Destination Load Balancing for Cisco Express Forwarding Traffic
• Load-Balancing Algorithms for Cisco Express Forwarding Traffic
Per-Destination Load Balancing for Cisco Express Forwarding Traffic
Per-destination load balancing allows the router to use multiple paths to achieve load sharing across
multiple source-destination host pairs. Packets for a given source-destination host pair are guaranteed to
take the same path, even if multiple paths are available. Traffic streams destined for different pairs tend
to take different paths.
Per-destination load balancing is enabled by default when you enable Cisco Express Forwarding. To use
per-destination load balancing, you do not perform any additional tasks once Cisco Express Forwarding
is enabled. Per-destination is the load-balancing method of choice for most situations.
Because per-destination load balancing depends on the statistical distribution of traffic, load sharing
becomes more effective as the number of source-destination host pairs increases.
You can use per-destination load balancing to ensure that packets for a given host pair arrive in order.
All packets intended for a certain host pair are routed over the same link (or links).
Typically, you disable per-destination load balancing when you want to enable per-packet load
balancing.
Load-Balancing Algorithms for Cisco Express Forwarding Traffic
The following load-balancing algorithms are provided for use with Cisco Express Forwarding traffic.
You select a load-balancing algorithm with the ip cef load-sharing algorithm command.
• Universal algorithm—The universal load-balancing algorithm allows each router on the network to
make a different load sharing decision for each source-destination address pair, which resolves
load-sharing imbalances. The router is set to perform universal load sharing by default.
• Include-ports algorithm—The include-ports algorithm allows you to use the Layer 4 source and
destination ports as part of the load-balancing decision. This method benefits traffic streams running
over equal cost paths that are not load shared because the majority of the traffic is between peer
addresses that use different port numbers, such as Real-Time Protocol (RTP) streams.
Note Cisco IOS Release 15.0(1)MR does not support the original or tunnel algorithms.
How to Configure a Load-Balancing Scheme for Cisco Express Forwarding
Traffic
Perform the following tasks to configure and fine-tune load balancing for Cisco Express Forwarding:
• Enabling or Disabling Cisco Express Forwarding Per-Destination Load Balancing, page 13-8
(optional)
• Selecting a Cisco Express Forwarding Load-Balancing Algorithm, page 13-8 (optional)