When multiple routing protocols offer a route for the same prefix, what part of the router is in charge of deciding which route to make active?

The Routing Table Manager (RTM) is the control plane process responsible for maintaining the routing information base (RIB). When multiple routing protocols, such as IS-IS, OSPF, or BGP, provide a route to the same destination prefix, the RTM selects the single best route. This selection is primarily based on the configured preference (administrative distance) for each protocol. The route from the protocol with the lowest preference value is chosen as the active route and is then installed into the forwarding information base (FIB) for use in packet forwarding.

A. The routing information base (RIB) is a database that stores all learned routes from all protocols; it is the repository of information, not the decision-making entity itself.

C. The equal cost multipath (ECMP) configuration is a feature that allows multiple best paths from a single, selected protocol to be used simultaneously, not for choosing between different protocols.

D. The forwarding information base (FIB) contains only the active routes that have already been selected by the RTM. It is the result of the decision, not the decision-maker.

1. Nokia 7750 SR OS Router Configuration Guide

Release 21.10.R1

Section: Routing Table Manager. This section describes the RTM's role in selecting the best route from various protocols based on preference and installing it into the forwarding table.

2. Nokia 7750 SR OS Basic System Configuration Guide

Release 21.10.R1

Section: Route Tables. This guide explains that the RTM manages the route tables (RIB) and is responsible for resolving best paths to be offered to the forwarding engine (FIB).