A prefix list can filter on which option?
- classful subnet and port
- prefix and prefix length
- prefix and port number
- protocol and prefix
Explanation: Prefix lists are specialized tools designed for route filtering that offer superior performance compared to traditional access lists. Their primary capability is the ability to filter routing updates based on both the network prefix and the prefix length.
The sources highlight several advantages and characteristics of prefix lists:
- Granular Matching: A prefix list can specify the exact size of a subnet mask or indicate a range within which the mask must fall to pass the test.
- Efficiency: The router transforms a prefix list into a tree structure, allowing it to determine a "permit" or "deny" verdict much faster than the sequential processing required by access lists.
- Specialization: While access lists were originally designed for packet filtering and later extended to routes, prefix lists are intended specifically for route filtering.
Options involving port numbers are incorrect because prefix lists operate at the routing level (Layer 3) to evaluate network addresses and masks, whereas port numbers are part of the transport layer (Layer 4) used for packet filtering.
Related exam: Modules 8 – 13: Checkpoint Exam: Network Routing Answers (CCNP ENCOR v9)
