Are you taking the CCNP Routing and Switching certification exam? If so, you’ll need to have the right amount of in-depth knowledge of the Cisco Express Forwarding (CEF), which is one of the switching techniques that you must know to pass the high-stakes test. Consider the overview below and prepare with a provider of CCNP training in the Philippines to master the technique before you take the exam.
The Purpose of Cisco Express Forwarding
CEF is a packet-switching method employed within Cisco routers. Its main purpose is to speed up packer switching and optimize packet forwarding.
Advantages of Cisco Express Forwarding
CEF offers the following advantages to Cisco routers:
- Scalability – When the dCEF mode is active, CEF can provide full switching capacity to each line card.
- Resilience – It provides an unparalleled level of switching stability and consistency to extensive dynamic networks.
- Enhanced Performance – Compared to fast switching route caching, CEF is no CPU-intensive. It lets the system dedicate more CPU processing power to other services.
A Short History of Process-Switching
Before CEF became the standard option it is known today, there were two known packet-switching options that were in use:
- Fast-switching is the most reliable packet-switching method before CEF. It employs the CPU to identify the destination only for the first packet. The information of the last point is stored with a fast-switching cache. The packets following the initial one are then switched using the cache instead of the CPU.
While it is a reliable packet-switching method, there have been certain complications that come with it. The cache is built on-demand and the first packet is constantly process-switched, which means that that the CPU will still be consumed and affect switching performance in the event of the high volume of traffic being received by the router.
- Process-switching is the slowest method, which is a given since it’s the first packet-switching method. With it, the CPU is involved in each and every forwarding decision.
Components of CEF
Information that is typically stored in a route cache is, in turn, typically stored in various data structures for CEF switching. These data structures offer optimized overviews to enable efficient packet forwarding, thanks to the two main components involved in this process. Instructors of the best Cisco training centers in the Philippines always tell their students to get to know both components before they take the test. Here’s a summary of each one:
- Adjacency Tables
CEF utilizes adjacency tables to analyze Layer 2 addressing information. The tables also retain Layer 2 next-hop addresses for all FIB entries.
- Forwarding Information Base (FIB)
FIB is an essential CEF component as it’s responsible for more of the decisions made regarding IP destination prefix-based switching. It is quite similar to an information base or routing table. It retains a mirror image of the forwarded information within the IP routing table. When topology developments or routing changes happen in the network, the updates that the IP routing table get are reflected in the FIB.
Keep in mind that this is only an overview of CEF. If you want to get an in-depth take of its essentials and expand your hands-on experience regarding the method, prepare with the best provider of CCNP training in the Philippines today. Enroll in one of AR Network Consulting’s certification courses! Click here to check out our programs.