IGRP protocol is a distance vector protocol developed by Cisco. Devices that use this protocol must be Cisco because it has been developed by Cisco. It has been developed mainly to overcome some deficiencies in RIPv1 and to have a protocol of Cisco company. It uses distance vector algorithms such as RIP (Routing Information Protocol) and is created by adding a few additions to the properties of the RIP. IGRP is a classful protocol like RIP.
The largest possible hop count in IGRP (the number of digits - the number of routers reached by the pack) is 255, and the number of digits is a significant improvement over the RIP, which is only 15. However, the hop feature is not the only feature used as a routing metric. Unlike RIP, IGRP also uses line delay, bandwidth, reliability, and load status as metrics. This gives network administrators great flexibility. Depending on the characteristics of the network, the network administrator can use the appropriate values ​​as a metric. Routers do not understand the bandwidth value in their serial interfaces when calculating metrics, they use the given value. If no fixed value is given, the default value of 1.5 Mbit is used.
The biggest difference between RIP and IGRP is "autonomous system" - the so-called autonomous system (AS). Routers with the same AS number can communicate in IGRP.
Features of IGRP
AD (Administrative Distance): It is the numbering and ordering of the paths required for the router to reach the neighboring router. Its value is 100. If RIP and IGRP are used on a router, the selection of the best path will be based on the selection of the IGRP protocol. Because the AD value of the RIP is 120.
Update Time (Update Timer): It is the time for sending updated messages. It is 90 seconds.
Invalid Timer: The time during which a referral becomes invalid. It is 270 seconds.
Hold down Timer: 280 sec.
Deletion Time (Flush timer): It is the time to delete an orientation from the table of the orientation. It is 630 seconds.
There is no support for VLSM (Variable Length Subnet Masking).
In the example below, 160.75.5.17 network is introduced to the router in a system with an AS number.
RouterA (config) #router igrp 1
RouterA (config-router) #network 160.75.5.17
EIGRP (Enhanced Interior Gateway Routing Protocol)
Although EIGRP routing protocol is similar in many ways to the IGRP protocol developed by Cisco with the failure of the IGRP protocol, it is a highly preferred protocol in the networks of Cisco devices thanks to its improved features. This protocol is also called Hybrid because it has the properties of Distance Vector and Line State protocols at the same time.
The largest possible number of "hop count" in EIGRP is 224. When calculating EIGRP metrics, it uses line delay, bandwidth, reliability, and load status as IGRP as metrics. In addition, security can be increased by encrypted authentication between routers using the MD5 crypto algorithm.
One of the most important advantages of this protocol is that it offers a high speed of transition between alternative routes. EIGRP uses DUAL (Diffusing Update Algorithm - Propagation Update Algorithm) algorithm as protocol algorithm. Routing is calculated with this algorithm and in case of a problem, it switches to previously calculated backup routing. There is no such feature in other routing protocols. This feature gives EIGRP a great speed.
One of the most important differences of this protocol from IGRP is that it does not update periodically like IGRP. When there is a change in the routing table, only the part that is the change, not the whole table, is sent to other routers and the network traffic is accelerated by using the bandwidth in the least way.
In EIGRP, not all network information is sent to neighboring routers. Thanks to the packages called Hello package, you can learn about the status of the neighboring router. The "Hello" package sends the package called "acknowledgement" (received) as "unicast" (received) and the routing table is updated accordingly. RTP (Reliable Transport Protocol) protocol developed by Cisco is used while performing these operations. When any changes are made to the network topology (such as adding a new router), the newly added router can quickly create the routing table thanks to the RTP protocol using update packages called Query (Query).
Reference: SYSNETTECHSolutions / https://www.sysnettechsolutions.com/en/
