Configure and troubleshoot basic operation and routing on Cisco devices

These questions are based on 642-816 – Interconnecting Cisco Networking Devices Part 2.


Objective: Configure and troubleshoot basic operation and routing on Cisco devices
Sub-Objective: Compare and contrast methods of routing and routing protocols


Single Answer, Multiple Choice


Open Shortest Path First (OSPF) routing protocol uses which metric for optimal path calculation?



  1. MTU
  2. Cost
  3. Delay
  4. Hop Count

Answer:
B. Cost


Tutorial:
OSPF routing protocol is a link-state routing protocol and uses cost as a metric for optimal path calculation. It is an open standard protocol based on Dijkstra’s shortest path first algorithm. As per the algorithm, lowest cost path is selected as the optimal route. In Cisco IOS’s implementation of OSPF protocol, the cost of an interface is inversely proportional to the bandwidth of that interface. Therefore, higher bandwidth indicates a lower cost, resulting in path selection.


Maximum Transmission Unit (MTU), bandwidth, delay, load and reliability form a composite metric used by Interior Gateway Routing Protocol (IGRP) and Enhanced Interior Gateway Routing Protocol (EIGRP). IGRP is a distance vector routing protocol developed by Cisco Systems. Enhanced IGRP (EIGRP) is a Cisco proprietary hybrid protocol having features of both distance vector and link state protocols.


Hop count metric is used by Routing Information Protocol (RIP). The lower the number of hops between the routers, the better the path.


Reference:
Cisco > Support > IP Routing > OSPF Design Guide
Cisco > Tech Notes > IGRP Metric
Home > Articles > Cisco Certification > CCNA > IP Access List Security for CCNA Exam #640-607

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