Specifications

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Chapter 13 Configuring Cisco Express Forwarding
Information About Cisco Express Forwarding
• Scalability—Cisco Express Forwarding offers full switching capacity at each line card when
distributed Cisco Express Forwarding mode is active. Distributed Cisco Express Forwarding is a
distributed switching mechanism that scales linearly with the number of interface cards and the
bandwidth installed in the router.
Note Distributed Cisco Express Forwarding is not currently supported on the Cisco MWR 2941.
• Resilience—Cisco Express Forwarding offers an unprecedented level of switching consistency and
stability in large dynamic networks. In dynamic networks, fast-switched cache entries are frequently
invalidated by routing changes. These changes can cause traffic to be process-switched through use
of the routing table, rather than fast switched through use of the route cache. Because the forwarding
information base (FIB) lookup table contains all known routes that exist in the routing table, it
eliminates the need for route cache maintenance and the steps involved with fast-switch or
process-switch forwarding. Cisco Express Forwarding can switch traffic more efficiently than
typical demand caching schemes.
You can use Cisco Express Forwarding in any part of a network. For example, Figure 13-1 shows Cisco
Express Forwarding being run on Cisco 12000 Series Internet routers at aggregation points at the core
of a network where traffic levels are high and performance is critical.
Figure 13-1 Cisco Express Forwarding Example
In a typical high-capacity Internet service provider (ISP) environment, Cisco 12000 Series Internet
routers function as aggregation devices at the core of the network and support links to Cisco 7500 series
routers or other feeder devices. Cisco Express Forwarding in these platforms at the network core
provides the performance and scalability that networks need to respond to continued growth and steadily
increasing network traffic. Cisco Express Forwarding is a distributed switching mechanism that scales
linearly with the number of interface cards and the bandwidth installed in the router.
Media Supported by Cisco Express Forwarding
Cisco Express Forwarding currently supports the following media:
• ATM/AAL5snap, ATM/AAL5mux, and ATM/AAL5nlpid
• Ethernet
• FDDI