Routing is an essential function that allows efficient flow of data between different devices. Within this context, two critical concepts are the RIB (Routing Information Base) and the FIB (Forwarding Information Base), which are fundamental to understanding how routers make routing decisions and direct traffic effectively.
At the end of the article you will find a small test that will allow you assess the knowledge acquired in this reading
What is the RIB?
The RIB, or Routing Information Base, is an internal routing table used by a router to store and manage information about the routes available on the network.
The RIB contains details about routes learned through dynamic routing protocols, static configurations, and any other relevant information about the network topology.
In essence, the RIB acts as a complete and dynamic knowledge base that the router uses to make routing decisions.
Each entry in the RIB includes information such as the destination address, netmask, next gateway (next-hop) and the associated metric.
How does the RIB work?
When a router receives routing information, either through routing protocols such as OSPF or BGP, or static configurations, it updates its RIB.
The RIB stores all the learned routes and selects the best route based on different criteria, such as the metric or the associated cost.
The RIB does not make direct decisions about where to direct traffic. Instead, serves as a repository of knowledge which the FIB uses to make forwarding decisions.
What is the IBF?
The IBF, or Forwarding Information Base, is closely tied to the RIB and is used to determine how to forward traffic based on information stored in the RIB.
While the RIB focuses on storing route information, the FIB focuses on forwarding actions.
The FIB contains a simplified version of the information stored in the RIB, with emphasis on the destination address and nearby gateway (next-hop).
The FIB is used to speed up the resending process, since it provides more concise and efficient information for decision making in real time.
The Relationship between RIB and FIB
The RIB and the FIB are intrinsically connected.
La RIB is continually updated as the network topology changes, while the FIB synchronizes with RIB to reflect these updates.
When a router needs to forward a packet, it consults the FIB to make quick and efficient decisions about how to route traffic.
Practical Examples of Using RIB and FIB
- Dynamic Routing: Dynamic routing protocols, such as OSPF or EIGRP, update the RIB with information about learned routes. The FIB uses this information to forward traffic efficiently.
- Static Routing: Static configurations also update the RIB, allowing network administrators to define specific routes. The FIB uses this information to direct traffic based on static configurations.
- Fast Convergence: The FIB allows for rapid convergence by making forwarding decisions based on more simplified and specific information than the RIB.
Botton line
The RIB and FIB are essential components in the routing architecture, working together to ensure efficient data flow and rapid decision making.
Understanding how these tables interact provides a solid foundation for effective network management and router performance optimization.
Brief knowledge quiz
What do you think of this article?
Do you dare to evaluate your learned knowledge?
Recommended books for this article
(Book) Networking with MikroTik RouterOS: A Practical Approach to Understanding and Implementing RouterOS
Study material for the MTCNA Certification Course, updated to RouterOS v7
RouterOS v7 Advanced Routing Book
Study material for the MTCRE Certification Course, updated to RouterOS v7