Eigrp and Ospf - Protocols

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The primary purpose of routing protocols is to for the router to make a table of available routes that exist across the entire enterprise network, some of the most common routing protocols include EIGRP and OSPF. While these routing protocols both aid in the transport of data across the network, they use very different approaches to how data is to be transmitted and received across all other routers within your networks.

        The first routing protocol were going to talk about is EIGRP, (Enhanced Interior Gateway Routing Protocol), this is a hybrid routing protocol made possible by Cisco systems development team, for routing many protocols across an enterprise Cisco network. It has the characteristics of both link state routing and protocols distance vector routing protocols. It is proprietary which means that it requires that you use only cisco brand routers within your network. “EIGRP will route the same protocols that IGRP and use the same composite metrics as IGRP to select a best path destination. As well there is the option to load balance traffic across equal or unequal metric cost paths” (Cisco.com). Summarization is automatic with an eigrp, at a network class address but it can be manually configured to summarize at the subnet boundaries as well. Redistribution between IGRP and EIGRP is automatic as well. There is support for variable length subnet masks and a hop count of 255. In addition to the basic router table EIGRP also use two other tables to keep track of network information. These tables are the neighbors table and the topology table.  The Purpose of the neighbor table is to keep a running record of the network information of all other routers that have a direct physical connection with this router. Routers that are connected to this router, through another router are not recorded in this table as they are not considered to be direct neighbors. The router topology table servers as a storage space for a list of the routes that it has learned from neighboring routing tables. Unlike the routing table, the topology table does not store all of the routes, but it does list all the routes that have been determined by EIGRP. The topology table also takes note of all of the metrics for each of the EIGRP routes that it records, the most reasonable, successor and the successors. All routes within the topology table are noted as "passive" or "active". Passive shows that EIGRP has made the determination that the path for the specific route and has finished processing. Active shows that EIGRP is still trying to calculate the best path for the section of the route. Pathways in the topology table are not usable by the router until they are inserted into the routing table. The topology table is never used by the router to forward traffic. Routes in the topology table will not be inserted into the routing table if they are active, are a feasible successor, or have a higher administrative distance than an equivalent path.