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Difficulty: EasyRouting Table Components

An network administrator reviews routing table entries using the `show ip route` command on a Cisco IOS router. Which two statements correctly describe components of an IPv4 routing table entry?

  1. Administrative distance indicates the trustworthiness of the route source, with lower values being preferred.Answer
  2. The metric is a value calculated by a routing protocol to select the best path among multiple routes to the same destination network.Answer
  3. C
    When forwarding a packet, the router compares administrative distance before evaluating subnet mask prefix length.
  4. D
    Routes marked with the source code 'S' represent dynamically learned OSPF routes.

Answer

The two correct statements are that administrative distance measures the trustworthiness of a routing source (with lower values preferred) and that metric is used by a routing protocol to select the best path to a destination network.
Administrative distance measures the trustworthiness of a routing source (where lower numbers represent greater trust), and metrics are used by individual routing protocols to identify the optimal path among available routes.

Step-by-Step Solution

1
Analyze the role of Administrative Distance (AD)
AD defines route trustworthiness from 0 (most trusted) to 255 (unbelievable/untrusted). Lower values are preferred.
AD helps the router choose which routing source to populate into the routing table when multiple sources offer the exact same destination network prefix.
2
Analyze the role of Metric
Metric measures path cost within a single routing protocol (e.g., OSPF cost, RIP hop count).
Routing protocols use metrics to evaluate competing paths to the same destination prefix and choose the best route.
3
Verify forwarding decision order and source codes
Longest prefix match is evaluated first during packet lookup, not AD. Source code 'S' stands for Static, while 'O' stands for OSPF.
This invalidates options suggesting AD precedes prefix length or misidentifying static routes as OSPF.

Key Concept

Routing Table Components and Metrics
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Topics

Routing Table Components

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