Interior Gateway Routing Protocol (IGRP) is a
distance vector interior gateway protocol (IGP) developed by
Cisco
Cisco Systems, Inc., commonly known as Cisco, is an American-based multinational digital communications technology conglomerate corporation headquartered in San Jose, California. Cisco develops, manufactures, and sells networking hardware, ...
. It is used by
routers to exchange
routing
Routing is the process of selecting a path for traffic in a network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched telephone netw ...
data within an
autonomous system.
IGRP is a
proprietary protocol
In telecommunications, a proprietary protocol is a communications protocol owned by a single organization or individual.
Intellectual property rights and enforcement
Ownership by a single organization gives the owner the ability to place restricti ...
. IGRP was created in part to overcome the limitations of
RIP
Rest in peace (RIP), a phrase from the Latin (), is sometimes used in traditional Christian services and prayers, such as in the Catholic, Lutheran, Anglican, and Methodist denominations, to wish the soul of a decedent eternal rest and peace.
...
(maximum hop count of only 15, and a single routing metric) when used within large networks. IGRP supports multiple metrics for each route, including
bandwidth
Bandwidth commonly refers to:
* Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range
* Bandwidth (computing), the rate of data transfer, bit rate or thr ...
,
delay
Delay (from Latin: dilatio) may refer to:
Arts, entertainment, and media
* ''Delay 1968'', a 1981 album by German experimental rock band Can
* ''The Delay'', a 2012 Uruguayan film
People
* B. H. DeLay (1891–1923), American aviator and acto ...
,
load
Load or LOAD may refer to:
Aeronautics and transportation
*Load factor (aeronautics), the ratio of the lift of an aircraft to its weight
*Passenger load factor, the ratio of revenue passenger miles to available seat miles of a particular transpo ...
, and
reliability
Reliability, reliable, or unreliable may refer to:
Science, technology, and mathematics Computing
* Data reliability (disambiguation), a property of some disk arrays in computer storage
* High availability
* Reliability (computer networking), a ...
; to compare two routes these metrics are combined into a single metric, using a formula which can be adjusted through the use of pre-set constants. By default, the IGRP composite metric is a sum of the segment delays and the lowest segment bandwidth. The maximum configurable hop count of IGRP-routed packets is 255 (default 100), and routing updates are
broadcast
Broadcasting is the distribution of audio or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum ( radio waves), in a one-to-many model. Broadcasting began ...
every 90 seconds (by default). IGRP uses
protocol number 9 for communication.
[{{cite web
, url=https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xml
, title=Assigned Internet Protocol Numbers
, publisher=]Internet Assigned Numbers Authority
The Internet Assigned Numbers Authority (IANA) is a standards organization that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System (DNS), media types, and other Interne ...
(IANA)
, access-date=18 June 2013
IGRP is considered a
classful routing protocol. Because the protocol has no field for a
subnet mask
A subnetwork or subnet is a logical subdivision of an IP network. Updated by RFC 6918. The practice of dividing a network into two or more networks is called subnetting.
Computers that belong to the same subnet are addressed with an identical ...
, the router assumes that all subnetwork addresses within the same Class A, Class B, or Class C network have the same subnet mask as the subnet mask configured for the interfaces in question. This contrasts with classless routing protocols that can use
variable length subnet masks. Classful protocols have become less popular as they are wasteful of
IP address space.
Advancement
In order to address the issues of address space and other factors, Cisco created
EIGRP
Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that is used on a computer network for automating routing decisions and configuration. The protocol was designed by Cisco Systems as a proprietary pr ...
(Enhanced Interior Gateway Routing Protocol). EIGRP adds support for
VLSM
Classless Inter-Domain Routing (CIDR ) is a method for allocating IP addresses and for IP routing. The Internet Engineering Task Force introduced CIDR in 1993 to replace the previous classful network addressing architecture on the Internet. Its g ...
(variable length subnet mask) and adds the
Diffusing Update Algorithm The diffusing update algorithm (DUAL) is the algorithm used by Cisco's EIGRP routing protocol to ensure that a given route is recalculated globally whenever it might cause a routing loop. It was developed by J.J. Garcia-Luna-Aceves at SRI Internati ...
(DUAL) in order to improve routing and provide a loopless environment. EIGRP has completely replaced IGRP, making IGRP an obsolete routing protocol. In Cisco IOS versions 12.3 and greater, IGRP is completely unsupported. In the new Cisco
CCNA
CCNA (Cisco Certified Network Associate) is an information technology (IT) certification from Cisco Systems. CCNA certification is an associate-level Cisco Career certification.
The Cisco exams have changed several times in response to the changin ...
curriculum (version 4), IGRP is mentioned only briefly, as an "obsolete protocol".
References
External links
Cisco - An Introduction to IGRPUS Patent 5,088,032 "Method and apparatus for routing communications among computer networks"
Cisco protocols
Routing protocols