CIDR or Classless Inter Domain Routing was developed to reduce the increasing size of routing tables of large routers, which was quite hard with classful routing. The memory usage of classful routing is enormous, which results in unreasonable expensive hadware. But also the performance was compromised, since large tables need to be looked up without a more dynamic IP interval mechanism, like CIDR imposes. Another problem with a classful setup is, that the bandwidth usage is quite high when routers exchange their routing information.