Route Aggregation

Internet Route Aggregation

Although the capability to assign small blocks of addresses helped extend the IPv4 public address space, this practice also introduced many more public subnets into the Internet, driving up the number of routes in Internet routing tables. At the same time, the number of hosts connected to the Internet, back in the 1990s, was increasing at a double-digit rate per month. Internet core routers could not have kept up with the rate of increase in the size of the IP routing tables.

The solution was, and still is today, to allocate numerically consecutive addresses—addresses that can be combined into a single route prefix/length—by geography and by ISP. These allocations significantly aid route summarization.