Supernetting (route aggregation)
Supernetting, also called route aggregation or route summarization, is the practice of combining several contiguous, same-size IP address blocks into one larger block that can be advertised as a single route. It's possible because of CIDR's prefix-length notation (RFC 4632, obsoleting the original CIDR documents RFC 1518 and RFC 1519): four contiguous /24 blocks that align on a /22 boundary can be announced as one /22 route instead of four separate /24 routes. Internet service providers rely on supernetting to keep the global BGP routing table from growing in proportion to every small allocation ever made; without it, routers would need to store and process far more routes. The tradeoff is that aggregation only works cleanly when the underlying blocks are contiguous and properly aligned, so allocations are usually planned around power-of-two boundaries. AdminKit's subnet calculator shows a block's boundaries, useful when checking whether adjacent blocks can be cleanly aggregated.
By AdminKit team, Netbase JSC · Updated