Based on the provided reference, the question is likely asking about the relationship between the Routing Information Base (RIB) and the Forwarding Information Base (FIB). Let's clarify these concepts:
Understanding RIB and FIB
- RIB (Routing Information Base): Think of this as a comprehensive database containing all known routing prefixes. It's built by various routing protocols.
- FIB (Forwarding Information Base): The FIB is a mirror copy of the routing table and one of two components that make up Cisco Express Forwarding (CEF). It is used for fast packet forwarding.
Analogy: Routing Protocols, Routing Table, RIB and FIB
You can think of routing protocols as different map services. Each map service might discover multiple routes to a particular address (destination). All of those routes from all of the different map services get put into the RIB. The routing table is the best routes from the RIB.
The FIB is a copy of the routing table for the fastest lookups possible.
Key Differences
| Feature | RIB | FIB |
|---|---|---|
| Purpose | Stores all known routing prefixes | Used for fast packet forwarding |
| Content | Contains multiple potential routes | Contains the best routes (from the Routing Table) |
| Protocol Info | Stores routing protocol data | Stores info for CEF |
| Update Source | Routing protocols (OSPF, EIGRP, etc.) | Routing Table |
In summary:
The RIB stores all possible routes, while the FIB, a mirror copy of the routing table, is optimized for fast packet forwarding. The FIB is a subset of the information stored in the routing table which, in turn, contains the best routes from the RIB.
