Route Summarization Can Combine Multiple Routing Table Entries Into a Single Entry.
An instance of road assemblage as a part of CIDR.
A supernetwork, or supernet, is an Net Protocol (IP) network that is formed by combination of multiple networks (or subnets) into a larger network. The new routing prefix for the combined network represents the elective networks in a single routing tabular array entry. The procedure of forming a supernet is called supernetting, prefix aggregation, route assemblage, or route summarization.
Supernetting within the Internet serves as a strategy to avert topological fragmentation of the IP address space past using a hierarchical allocation system that delegates control of segments of address space to regional network service providers.[i] This method facilitates regional route aggregation.
The benefits of supernetting are conservation of address space and efficiencies gained in routers in terms of retentiveness storage of route information and processing overhead when matching routes. Supernetting, however, can introduce interoperability issues and other risks.[2]
Overview [edit]
In Net networking terminology, a supernet is a block of contiguous subnetworks addressed as a single subnet from the perspective of the larger network. Supernets are always larger than their component networks. Supernetting is the process of aggregating routes to multiple smaller networks, thus saving storage space in the routing table and simplifying routing decisions and reducing routing advertisements to neighboring gateways. Supernetting has helped accost the increasing size of routing tables as the Internet has expanded.
Supernetting in large, complex networks can isolate topology changes from other routers. This tin can improve the stability of the network by limiting the propagation of routing traffic in the outcome of a network link failure. For example, if a router only advertises a summary route to the next router, and so it does not need to advertise whatsoever changes to specific subnets within the summarized range. This can significantly reduce any unnecessary routing updates following a topology change. Hence, it increases the speed of convergence resulting in a more stable environment.
Protocol requirements [edit]
Supernetting requires the use of routing protocols that support Classless Inter-Domain Routing (CIDR). Interior Gateway Routing Protocol, Exterior Gateway Protocol and version one of the Routing Information Protocol (RIPv1) assume classful addressing, and therefore cannot transmit the subnet mask data required for supernetting.
Enhanced Interior Gateway Routing Protocol (EIGRP) is a classless routing protocol supporting CIDR. By default, EIGRP summarizes the routes inside the routing table and forrard these summarized routes to its peers. This may accept an adverse impact in heterogeneous routing environments with discontiguous subnets.[3]
Other routing protocols with CIDR back up include RIPv2, Open up Shortest Path First, EIGRP, IS-IS and Border Gateway Protocol.
Examples [edit]
A visitor that operates 150 bookkeeping services in each of 50 districts has a router in each role continued with a Frame Relay link to its corporate headquarters. Without supernetting, the routing tabular array on any given router might have to account for 150 routers in each of the 50 districts, or 7500 different networks. Nonetheless, if a hierarchical addressing arrangement is implemented with supernetting, and so each district has a centralized site as interconnection bespeak. Each route is summarized before being advertised to other districts. Each router now only recognizes its own subnet and the other 49 summarized routes.
The determination of the summary route on a router involves the recognition of the number of highest-club bits that match all addresses. The summary road is calculated as follows. A router has the following networks in its routing tabular array:
192.168.98.0 192.168.99.0 192.168.100.0 192.168.101.0 192.168.102.0 192.168.105.0
Firstly, the addresses are converted to binary format and aligned in a list:
| Address | Commencement Octet | 2d Octet | Third Octet | Fourth Octet |
|---|---|---|---|---|
| 192.168.98.0 | 11000000 | 10101000 | 01100010 | 00000000 |
| 192.168.99.0 | 11000000 | 10101000 | 01100011 | 00000000 |
| 192.168.100.0 | 11000000 | 10101000 | 01100100 | 00000000 |
| 192.168.101.0 | 11000000 | 10101000 | 01100101 | 00000000 |
| 192.168.102.0 | 11000000 | 10101000 | 01100110 | 00000000 |
| 192.168.105.0 | 11000000 | 10101000 | 01101001 | 00000000 |
Secondly, the bits at which the mutual design of digits ends are located. These mutual bits are shown in cherry. Lastly, the number of common $.25 is counted. The summary route is found by setting the remaining bits to goose egg, as shown below. Information technology is followed by a slash then the number of common bits.
| Showtime Octet | Second Octet | Tertiary Octet | Fourth Octet | Address | Netmask |
|---|---|---|---|---|---|
| 11000000 | 10101000 | 01100000 | 00000000 | 192.168.96.0 | /xx |
The summarized route is 192.168.96.0/xx. The subnet mask is 255.255.240.0.
This summarized route also contains networks that were not in the summarized grouping, namely, 192.168.96.0, 192.168.97.0, 192.168.103.0, 192.168.104.0, 192.168.106.0, 192.168.107.0, 192.168.108.0, 192.168.109.0, 192.168.110.0, and 192.168.111.0. It must be assured that the missing network prefixes do non exist outside of this route.
In another example, an Internet service provider is assigned a block of IP addresses past a regional Internet registry (RIR) of 172.i.0.0 to 172.one.255.255. The ISP might then assign subnetworks to each of their downstream clients, e.g., Customer A will accept the range 172.ane.ane.0 to 172.ane.1.255, Customer B would receive the range 172.i.2.0 to 172.one.2.255 and Customer C would receive the range 172.i.three.0 to 172.1.three.255, so on. Instead of an entry for each of the subnets 172.ane.one.10 and 172.1.2.10, etc., the ISP could aggregate the entire 172.i.ten.x address range and advertise the network 172.1.0.0/16 on the Internet community, which would reduce the number of entries in the global routing table.
Risks [edit]
The following supernetting risks take been identified:[ii]
- Supernetting is implemented in different ways on different routers
- Supernetting on one router interface tin influence how routes are advertised on other interfaces of the same router
- In the presence of supernetting, detecting a persistent routing loop becomes a difficult problem
Run across too [edit]
- Provider-aggregatable address space
- Provider-independent address space
References [edit]
- Notes
- ^ RFC 1338, Supernetting: an Address Assignment and Aggregation Strategy, V. Fuller, T. Li, J. Yu, K. Varadhan (June 1992)
- ^ a b Franck Le; Geoffrey G. Xie; Hui Zhang (2011). "On Route Aggregation" (PDF). ACM. Retrieved 2013-01-x .
- ^ Antonio Maciá (xiii February 2012). "EIGRP Summarization Issues". Retrieved 2020-07-31 .
- Bibliography
- Comer, Douglas E. (2006). Internetworking with TCP/IP, 5, Prentice Hall: Upper Saddle River, NJ.
External links [edit]
- The Supernetting/CIDR Chart
- IP Address Subnetting Tutorial
- Netmatics Supernet Calculator - A complimentary web-based tool for route assemblage
- Road Summarization Figurer
- Supernet Examples and How to Summate Supernets
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Source: https://en.wikipedia.org/wiki/Supernetwork
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