Grouping IP addresses into subnets and supernets is a fundamental aspect of IP address management. Enabling network admins to break up and aggregate different IP groups of their massive network address space into manageable entities, IP subnetting and supernetting have become core components of effective network address space management. The reason why creating a supernet helps the administrator utilize the available IP address space more efficiently is because of the simplified routing. These supernets are beneficial especially when there are multiple networks with limited number of IPs within each network.
Understanding the nuances of supernetting and the key differences between supernets and subnets is critical to designing and managing your IT ecosystem's network address space. A proper supernetting solution can help you address these nuances, and build network resiliency within your network. On this page, we will discuss the following:
Supernets or supernetworks are formed by aggregating several IP subnets with contiguous (i.e., adjacent or adjoining) address ranges into one large network with a single Classless Inter-Domain Routing (CIDR) prefix. This new, shorter prefix represents the supernet and its associated subnets as one entry in the routing table entries.
For example, consider four subnets:
10.12.1.0 /24
10.12.2.0 /24
10.12.3.0 /24
10.12.4.0 /24
To create a supernet for these subnets with contiguous IP prefixes, the network admins can use the prefix 10.12.0.0 /21, which covers all these subnets. Note that the routing prefix of the supernet is the same as the collection of routing prefixes of its associated subnets.
Instead of advertising the routes of each of the four subnets separately, with supernetting, the routes to these subnets can be advertised as a single aggregated supernet route. This simplifies network address space management and reduces the number of routing table entries. This in turn reduces the network routing overhead, router process overhead, and routing device requirements, helping the router store information efficiently by combining several independent routes.
The process of creating a supernet is called supernetting, route aggregation, or route summarization.
In enterprise networks with a massive IP address space, IP subnetting creates multiple smaller networks by lengthening the IP address mask. As the network scales, the number of subnets formed increases the number of routing table entries, eventually causing a router overload. To avoid this scenario and optimize network routing, as discussed above, the subnets should be aggregated into one supernet.
Supernets and route aggregation rely on classless routing to transmit the subnet mask information. The two protocols that support this are:
Other TCP and IP routing protocols, such as Interior Gateway Routing Protocol (IGRP) and Routing Information Protocol (RIP), only support classful routing and thus do not support supernets or the route aggregation process.
Among its several benefits, supernetting significantly reduces the number of routing updates required. With each route, as the packet size increases, so does the amount of bandwidth required to transfer it, leaving less bandwidth available for other data transfers. Supernetting avoids this hassle by following the three processes of:
Only Supernetting your network is not enough, it has to be managed constantly to make sure there are no network outages. This can be done by using a supernetting tool like ManageEngine OpUtils, which helps you manage the supernets in your organization efficiently.
As discussed earlier, to create a supernet solution, you need to group multiple smaller subnets into one larger network. But to effectively do this, it is necessary to have a good understanding of how IP subnetting and IP addressing works. Network admins can create supernets in three simple steps:
Prerequisite: The subnets should be contiguous.
Not all subnets need to be aggregated into a supernet. Network admins are advised to carefully analyze their network address space and routing loads before creating supernets.
Let us assume that an organization has the following four subnets and that the network admin has choosen to aggregate them into a supernet:
10.12.1.0 /24
10.12.2.0 /24
10.12.3.0 /24
10.12.4.0 /24
Translate the numerical IP addresses of the subnets' IDs into their binary form.
This translates the subnets above to the following:
10.12.1.0 /24 = 00001010.00001100.00000001.00000000
10.12.2.0 /24 = 00001010.00001100.00000010.00000000
10.12.3.0 /24 = 00001010.00001100.00000011.00000000
10.12.4.0 /24 = 00001010.00001100.00000100.00000000
Now, in the binary form, find the longest matching bits from left to right and add zeros for the remaining bits. Adding zeros converts the network bits of the aggregated subnets into host bits.
In this case, the result would be 00001010.00001100.00000000.00000000. Which translates to the following network ID: 10.12.0.0. This is the summarized route of the supernet that will be advertised.
To identify the mask, replace the matching bits identified in Step 2 with ones.
In this case, it would be 11111111.11111111.11111000.00000000. Which translates to the following new mask: 255.255.248.0. Thus, our new summarized route or supernet address is 10.12.0.0 / 21.
Subnetting and supernetting are two different techniques used in IP networking to optimize IP address usage and routing efficiency, respectively. However, there are significant differences between the two. Here are 7 key differences between subnetting and supernetting:
| Factor | Subnets | Supernets |
|---|---|---|
| 1. Core purpose | Decrease address depletion | Improve routing efficiency |
| 2. Network segmentation | Segment the IP address space into smaller, more manageable networks | Aggregate smaller networks to be represented as a single networking entity |
| 3. IP address bits | Increase the network's address bits by shifting the network mask bits towards the right | Increase the host's address bits by shifting the network mask bits towards the left |
| 4. IP management techniques | Rely on variable-length subnet mask (VLSM) and fixed-length subnet mask (FLSM) techniques | Rely on the CIDR technique |
| 5. Addressing restrictions | Require all IP-associated devices within the subnet to use the same subnet mask |
|
| 6. Security | Can limit network communication between different devices by creating several isolated subnets | Do not offer this capability |
| 7. Use cases |
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Before choosing to create supernets, it is important to carefully evaluate their pros and cons with respect to your network. While supernets offer several benefits, careful planning and choosing a powerful supernet solution is required to avoid their potential drawbacks.
In a nutshell, supernet provides a scalable and efficient way to manage IP addresses and optimize network routing.
ManageEngine OpUtils' is a supernet tool that enables you to leverage a comprehensive IP address manager and advanced IP scanner to track, monitor, and manage your supernets with ease. This holistic supernet monitor tool offers in-depth insights into all your network supernets and associated subnets, with real-time insights into the IP utilization, status, and availability metrics.
Group and monitor your network address space into subnets, supernets, and IP address groups with a hierarchical Tree View. Use OpUtils' capabilities to drill down to the physical location of specific IPs to simplify IP address management. Set up proactive subnet monitoring with customized scan schedules for different IP groups.
Detect IP conflicts, prevent rogue devices, and enable end-to-end switch port mapping with OpUtils.
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