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Difficulty: EasyRouting Concepts and Dynamic Routing Protocols

A network router receives route advertisements for the same destination network from two different dynamic routing protocols: OSPF and RIP. The router automatically prefers the route learned through OSPF over the route learned through RIP. Which criterion does the router use first to compare the trustworthiness of these different routing protocols?

  1. Administrative distanceAnswer
  2. B
    OSI Layer 3 PDU frame encapsulation type
  3. C
    Default gateway subnet configuration
  4. D
    Access Control List implicit deny rules

Answer

Administrative distance is used by routers to evaluate the trustworthiness of routes learned via different routing sources.
Administrative distance (AD) is a rating of trustworthiness of a routing information source on a scale from 0 to 255. A lower value signifies a more reliable protocol. Since OSPF has a lower administrative distance (110) than RIP (120), the router prefers the OSPF path.

Step-by-Step Solution

1
Identify the scenario requirement
The router has two routes to the same network from different sources (OSPF and RIP).
When multiple routes to a single network are learned via different protocols, the router must decide which source is more trustworthy.
2
Evaluate protocol preference metric
Administrative distance (AD) is evaluated first.
AD defines trustworthiness; lower AD values mean higher believability (OSPF AD = 110, RIP AD = 120).

Key Concept

Administrative Distance in Dynamic Routing
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Topics

Routing Concepts and Dynamic Routing Protocols

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