VLSM and Route Summarization

Variable Length Subnet Mask (VLSM) and Route Summarization are techniques used in IP network design and routing to improve network scalability, reduce routing table size and make better use of IP address space.

VLSM is the ability to use different subnet mask lengths within a single network. This allows for more efficient use of IP address space by allocating smaller subnets to smaller network segments and larger subnets to larger network segments. For example, a network administrator can allocate a /26 subnet mask to a network with 30 hosts and a /24 subnet mask to a network with 150 hosts.

Route summarization is the process of aggregating multiple routes into a single summary route. This reduces the size of the routing table, improves routing efficiency and reduces the amount of processing required by routers. For example, if a router has multiple subnets that are all advertised separately, route summarization can be used to aggregate these subnets into a single route. Together, VLSM and route summarization can greatly improve the efficiency and scalability of IP networks. By using VLSM, network administrators can make better use of IP address space and avoid wasting IP addresses. By using route summarization, routers can reduce the size of the routing table and improve routing efficiency, particularly in large networks with many subnets.