Deploying Technology in the Campus Infrastructure Module
Designing a hierarchical IP addressing scheme

Hierarchical network addressing means that IP network numbers are applied to the network segments or VLANs in an orderly fashion that takes into consideration the network as a whole. Blocks of contiguous network addresses are reserved for, and configured on devices in a specific area of the network.

Here are some benefits of hierarchical addressing:

  • Ease of Management and Troubleshooting – Hierarchical addressing groups network addresses contiguously. Network management and troubleshooting is more efficient as a well-known IP addressing scheme will make problem components easier to locate.
  • Minimize Error – Orderly network address assignment can minimize error and duplicate address assignment.
  • Reduced number of routing table entries – In a hierarchical addressing plan, routing protocols are able to invoke route summarization which allows a single routing table entry to represent a collection of IP network numbers. Route summarization makes routing table entries manageable and provides the following benefits:
    • Reduced number of CPU cycles when recalculating a routing table or sorting through the routing table entries to find a match
    • Reduced router memory requirements
    • Faster convergence after a change in the network
    • Easier troubleshooting

Guidelines for Applying IP Address Space in the Enterprise Network
The Enterprise Composite Network Model provides a modular framework for designing and deploying networks. It also provides the ideal structure for overlaying a hierarchical IP addressing scheme. Some guidelines to follow are:

  • Design the IP addressing scheme so that blocks of 4, 8, 16, 32, or 64 contiguous network numbers can be assigned to the subnets in a given Building Distribution and Access switch block.
  • At the Building Distribution layer, continue to assign network numbers contiguously out toward to the Access Layer devices.
  • Have a single IP subnet correspond with a single VLAN.
  • Subnet at the same binary value on all network numbers avoiding variable length subnet masks when possible in order to minimize error and confusion when troubleshooting or configuring new devices and segments