Question

Difficulty: HardRouting Table Components

Match each component or prefix notation from a Cisco IOS routing table output to its correct technical characteristic or forwarding behavior.

  • Code prefix 'D EX' in: D EX 192.168.50.0/24 [170/2578560] via 10.1.1.2Identifies an external EIGRP learned route assigned a default Administrative Distance of 170
  • Bracketed notation '[110/65]' in: O 10.1.4.0/24 [110/65] via 10.1.12.1Defines the Administrative Distance of 110 followed by the OSPF path metric cost of 65
  • Prefix '192.168.10.0/28' vs '192.168.10.0/24' when forwarding to 192.168.10.14Selected for traffic forwarding regardless of Administrative Distance due to Longest Prefix Match rules
  • Code prefix 'C' in: C 172.16.1.0/24 is directly connected, GigabitEthernet0/0Indicates a directly connected subnet configured on an operational interface with an Administrative Distance of 0

Answer

Each routing table notation matches its corresponding definition based on Cisco IOS routing table syntax and path determination rules: 'D EX' matches external EIGRP with AD 170, '[110/65]' matches AD 110 and metric 65, the '/28' prefix matches the Longest Prefix Match rule, and 'C' matches a directly connected network with AD 0.
Each routing table component directly corresponds to Cisco IOS routing table syntax and path determination logic. 'D EX' signifies EIGRP external routes (AD 170); bracketed numbers '[110/65]' display Administrative Distance followed by Metric; destination matching favors the longest subnet mask (/28 over /24); and 'C' represents directly connected routes with an AD of 0.

Step-by-Step Solution

1
Analyze routing table protocol codes
Identify 'D EX' as EIGRP External (AD 170) and 'C' as Connected (AD 0).
Cisco IOS routing tables use specific legend codes to indicate how routes were learned.
2
Interpret numerical brackets [AD/Metric]
Confirm '[110/65]' represents Administrative Distance 110 (OSPF) and a cost metric of 65.
The first number in brackets is always the Administrative Distance and the second is the route metric.
3
Apply forwarding logic to destination lookup
Determine that the /28 route is selected over /24 because 28 matching bits exceeds 24 matching bits.
Longest prefix matching (LPM) is the fundamental rule evaluated before comparing administrative distance or metric.

Key Concept

Interpretation of Cisco IOS Routing Table Components and Forwarding Decision Logic
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