CIDR helps reduce routing table size by enabling which of the following?

• A. Subnetting
• B. DHCP scope aggregation
• C. Route summarization
• D. Broadcast domain consolidation

Answer: (C)

The main idea being tested is route summarization. CIDR lets you use prefixes of varying lengths, so you can group several adjacent networks into one larger, summarized route. When you advertise a single summary route (for example, a /22 that covers four /24s) instead of listing each individual subnet, routers have fewer entries to store and look up, which reduces the size of the routing table and speeds forwarding decisions. For instance, four neighboring /24 networks like 10.0.0.0/24 through 10.0.3.0/24 can be represented as a single 10.0.0.0/22 route if the aggregation aligns, and packets to any of those subnets will still reach the correct next hop. Subnetting actually creates more routes by dividing networks into smaller pieces, DHCP scope aggregation isn’t the CIDR function that reduces routing entries, and consolidating broadcast domains relates to layer 2 traffic, not routing table size.