Which statement about CIDR and routing tables is true?

• A. CIDR requires more routes to be installed in the routing table.
• B. CIDR prevents routing table aggregation.
• C. CIDR enables route aggregation to reduce routing table size.
• D. CIDR is a technique used only for IPv6.

Answer: (C)

CIDR enables route aggregation by allowing multiple networks to be advertised as a single route, which reduces the size of the routing table. When networks share a common prefix, you can summarize them with one longer-prefix entry (for example, a single /19 or /16) rather than listing each individual network. This keeps lookups fast and conserves memory in routers, which is essential as the network grows. Routing relies on the longest-prefix match, so the aggregate must accurately cover only the intended addresses; otherwise, reachability could be affected, so summarization is typically done where networks are contiguous within the same address space and aligned with a common boundary.

So this statement is true because CIDR, through prefix-based addressing, makes it possible to combine many routes into a single summarized route, directly reducing the routing table size.