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I have a strong confusion on this whether LPM is done in Data or Control Plane. My thoughts on this is as follows if its in data plane, we will have to do it for every packet hence we will have a reduced speed for forwarding. What I believe is that we can do everything in control plane and program the hardware after adding an identifier for the flow. Then on we need to just look at the flow identifier and forward the traffic without further lookup.

Is my idea correct ?

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Basically, the control plane is for data destined to the router itself (e.g. routing protocol updates), while the forwarding (data) plane controls what goes through the router. The forwarding plane can make decisions based on what is learned in the control plane, but the control plane itself doesn't make the forwarding decisions.

It sounds like you are sort of describing layer-3 switching. One thing to understand is that, ideally, each packet is switched independently of any other packets. You may want to study process switching vs. other switching methods. There are many documents, e.g. How to Choose the Best Router Switching Path for Your Network, which describe the various switching methods available, but this is vendor-dependent.

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Longest Prefix Match relates to IP, or layer 3, forwarding. There is no such thing as longest prefix match for MAC (layer2) addresses.

Control plane and data plane are unrelated concepts.

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Longest prefix mstching is done to forward ip packets, this is data plane function. Routing tables made using routing alogs contains a list of network prefixes , this is done in control plane.

Thanks.

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Longest prefix mstching is done to forward ip packets, this is data plane function. Routing tables made using routing alogs contains a list of network prefixes , this is done in control plane.

Thanks.

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  • This post is duplicate...
    – Zac67
    May 20 '20 at 12:30

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