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