200-301 · Question #979
Refer to the exhibit. Which entry is the longest prefix match for host IP address 192.168.10.5?
The correct answer is B. 2. This question requires identifying the most specific routing table entry that matches a given destination IP address.
Question
Refer to the exhibit. Which entry is the longest prefix match for host IP address 192.168.10.5?
Exhibits
Options
- A1
- B2
- C3
- D4
How the community answered
(45 responses)- A4% (2)
- B73% (33)
- C7% (3)
- D16% (7)
Why each option
This question requires identifying the most specific routing table entry that matches a given destination IP address.
Entry 1 would represent a less specific route (shorter prefix) than Entry 2 if both match the destination.
The longest prefix match rule dictates that the router selects the route with the most specific subnet mask (longest prefix) that includes the destination IP address. Entry 2 must correspond to a prefix length that is longer than the other matching entries while still encompassing 192.168.10.5.
Entry 3 would represent a less specific route (shorter prefix) than Entry 2 if both match the destination.
Entry 4 would represent a less specific route (shorter prefix) than Entry 2 if both match the destination.
Concept tested: Longest prefix match routing principle
Source: https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/23018-bgp-longest-match.html
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