Supernetting is the opposite of Subnetting. In subnetting, a single big network is divided into multiple smaller subnetworks. In Supernetting, multiple networks are combined into a bigger network termed as a Supernetwork or Supernet.
Supernetting is mainly used in Route Summarization, where routes to multiple networks with similar network prefixes are combined into a single routing entry, with the routing entry pointing to a Super network, encompassing all the networks. This in turn significantly reduces the size of routing tables and also the size of routing updates exchanged by routing protocols.
- When multiple networks are combined to form a bigger network, it is termed as super-netting
- Super netting is used in route aggregation to reduce the size of routing tables and routing table updates
There are some points which should be kept in mind while supernetting:
- All the Networks should be contiguous.
- The block size of every networks should be equal and must be in form of 2n.
- First Network id should be exactly divisible by whole size of supernet.
Example – Suppose 4 small networks of class C:
220.127.116.11, 18.104.22.168, 22.214.171.124, 126.96.36.199
Build a bigger network which have a single Network Id.
Explanation – Before Supernetting routing table will be look like as:
|Network Id||Subnet Mask||Interface|
First, lets check whether three condition are satisfied or not:
- Contiguous: You can easily see that all network are contiguous all having size 256 hosts.
Range of first Network from 188.8.131.52 to 184.108.40.206. If you add 1 in last IP address of first network that is 220.127.116.11 + 0.0.0.1, you will get the next network id that is 18.104.22.168. Similarly, check that all network are contiguous.
- Equal size of all network: As all networks are of class C, so all of the have a size of 256 which in turn equal to 28.
- First IP address exactly divisible by total size: When a binary number is divided by 2n then last n bits are the remainder. Hence in order to prove that first IP address is exactly divisible by while size of Supernet Network. You can check that if last n v=bits are 0 or not.
In given example first IP is 22.214.171.124 and whole size of supernet is 4*28 = 210. If last 10 bits of first IP address are zero then IP will be divisible.
Last 10 bits of first IP address are zero (highlighted by green color). So 3rd condition is also satisfied.
- Control and reduce network traffic
- Helpful to solve the problem of lacking IP addresses
- Minimizes the routing table
Therefore, you can join all these 4 networks and can make a Supernet. New Supernet Id will be 126.96.36.199.
Advantages of Supernetting –
Disadvantages of Supernetting –
- It cannot cover different area of network when combined
- All the networks should be in same class and all IP should be contiguous
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.
- Traceroute in Network Layer
- Fragmentation at Network Layer
- Design Issues in Network Layer
- Network Layer Services- Packetizing, Routing and Forwarding
- Difference between Secure Socket Layer (SSL) and Transport Layer Security (TLS)
- Difference between Subnetting and Supernetting
- Difference between layer-2 and layer-3 switches
- Cisco Discovery Protocol (CDP) and Link Layer Discovery Protocol (LLDP) in Data Link Layer
- Basic Network Attacks in Computer Network
- TCP and UDP in Transport Layer
- Transport Layer responsibilities
- Devices used in each layer of TCP/IP model
- Secure Socket Layer (SSL)
- Protocols in Application Layer
- Transport Layer Security (TLS)
- Switch functions at layer 2
- Framing in Data Link Layer
- Difference between Router and Layer-3 Switch
- Design Issues in Presentation Layer
- Session Layer Messaging Protocols in IoT
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to firstname.lastname@example.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.