How a router works: using Control Plane and Data Plane

How a router works: using Control Plane and Data Plane

I will explain (with few words) how a router works using Control Plane and Data Plane, including MPLS.

The complete routing table is stored in the Control Plane.

All routes learned from OSPF areas or RIP hop or AS from BGP for example.

This is called RIB = Routing Information Base. 

In the same way, all labels learned via LDP (MPLS) are stored in the Control Plane.

This is called LIB = Label Information Base.

CEF (Cisco Express Forwarding) is a table localized at Data Plane that shows the best route for a specific destination.

For example, if you have the same route for the destination 10.10.10.10/32 learned via OSPF (metric 110) or via iBGP (metric 200), the command "show ip cef" will show only the best route: in this case via OSPF.

The best routing for a destination is stored at FIB = Forwarding Information Base.

The best label for a destination is stored at LFIB = Label forwarding Information Base.

Control Plane is near the software.

Data Plane is near the hardware (faster).

A router decision is faster processed using Data Plane.

The picture below shows a relationship between the tables:

I will show the differences using my LAB. Look the topology below and watch my video: