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Difficulty: MediumRouting Table Components

Match each IPv4 routing table entry from a Cisco IOS 'show ip route' display to its correct protocol source classification and administrative properties.

  • D 192.168.10.0/24 [90/2170112] via 10.1.1.2Internal EIGRP route with default administrative distance of 90 and composite metric of 2170112
  • O 172.16.1.0/24 [110/20] via 10.1.1.6OSPF route with default administrative distance of 110 and cost metric of 20
  • S 10.2.2.0/24 [1/0] via 10.1.1.2Static route with administrative distance of 1 forwarding via next-hop 10.1.1.2
  • C 10.1.1.0/30 is directly connected, GigabitEthernet0/0Connected network route automatically installed with administrative distance of 0

Answer

Each routing table entry matches its corresponding protocol code, administrative distance, and metric: 'D' maps to Internal EIGRP (AD 90), 'O' maps to OSPF (AD 110), 'S' maps to Static (AD 1), and 'C' maps to Directly Connected (AD 0).
Routing table entries display their learning source code followed by the prefix, bracketed administrative distance and metric values [AD/Metric], next-hop IP, and outgoing interface. Code D identifies EIGRP (default AD 90), code O identifies OSPF (default AD 110), code S identifies Static routes (default AD 1), and code C identifies Connected networks (AD 0).

Step-by-Step Solution

1
Identify the protocol code prefix at the start of each routing entry.
D corresponds to EIGRP, O corresponds to OSPF, S corresponds to Static, and C corresponds to Connected.
Cisco IOS routing tables use single-letter prefix codes to identify how each route was learned.
2
Parse the bracketed values [Administrative Distance / Metric] for dynamically learned and static routes.
The first number inside brackets represents Administrative Distance (AD), and the second number represents the protocol metric.
AD measures route source trustworthiness while metric determines path preference within the protocol.
3
Match each entry to its exact functional description based on AD and metric values.
Entry with code D matches EIGRP (AD 90), entry with code O matches OSPF (AD 110), entry with code S matches Static (AD 1), and entry with code C matches Directly Connected (AD 0).
Each routing protocol has standard default administrative distance values recognized by Cisco IOS.

Key Concept

Routing Table Components and Source Codes
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Topics

Routing Table Components

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