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Routing & Switching · Intermediate

Process Switching

The slowest Cisco forwarding method, where the CPU performs a full routing lookup for every packet.

Definition

Process switching handles each packet in software and is used today only for traffic that cannot be CEF switched, such as packets needing special handling or punted to the CPU. Historically it was followed by fast switching (route cache) and then CEF. High process-switched traffic shows as high CPU in the IP Input process.

Example

show processes cpu sorted shows high IP Input utilization when packets are process switched.

Exam tip

Exams order the methods from slowest to fastest: process switching, fast switching, CEF.

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