Difference between revisions of "CCNA Explorer 2 Introduction to Dynamic Routing Protocols"
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m (New page: =Introduction and Advantages= ==Perspective and Background== {| |800px|left|thumb|History |} ==Network discovery and routing table maintenance== '''The purpose ...) |
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==Classful and Classless== | ==Classful and Classless== | ||
| + | {| | ||
| + | |[[Image:ScreenShot747.jpg|800px|left|thumb|Classful vs. Classless]] | ||
| + | |} | ||
| + | ==Convergence== | ||
| + | {| | ||
| + | |[[Image:ScreenShot748.jpg|800px|left|thumb|Convergence]] | ||
| + | |} | ||
| + | =Metrics= | ||
| + | ==Purpose of a Metric== | ||
| + | {| | ||
| + | |[[Image:ScreenShot749.jpg|800px|left|thumb|Metric]] | ||
| + | |} | ||
| + | ==Metrics and Routing Protocols== | ||
| + | The metric for each routing protocol is: | ||
| + | *'''RIP:''' Hop count - Best path is chosen by the route with the lowest hop count. | ||
| + | *'''IGRP and EIGRP:''' Bandwidth, Delay, Reliability, and Load - Best path is chosen by the route with the smallest composite metric value calculated from these multiple parameters. By default, only bandwidth and delay are used. | ||
| + | *'''IS-IS and OSPF:''' Cost - Best path is chosen by the route with the lowest cost. . Cisco's implementation of OSPF uses bandwidth. IS-IS is discussed in CCNP. | ||
| + | Metric used in IP routing protocols: | ||
| + | *'''Hop count''' - A simple metric that counts the number of routers a packet must traverse | ||
| + | *'''Bandwidth''' - Influences path selection by preferring the path with the highest bandwidth | ||
| + | *'''Load''' - Considers the traffic utilization of a certain link | ||
| + | *'''Delay''' - Considers the time a packet takes to traverse a path | ||
| + | *'''Reliability''' - Assesses the probability of a link failure, calculated from the interface error count or previous link failures | ||
| + | *'''Cost''' - A value determined either by the IOS or by the network administrator to indicate preference for a route. Cost can represent a metric, a combination of metrics or a policy. | ||
| + | {| | ||
| + | |[[Image:ScreenShot750.jpg|800px|left|thumb|Show ip Route]] | ||
| + | |} | ||
| + | ==Load Balancing== | ||
| + | {| | ||
| + | |[[Image:ScreenShot751.jpg|800px|left|thumb|Equal Cost Load Balancing]] | ||
| + | |} | ||
| + | =Administrativ Distance= | ||
| + | ==Purpose of Administrative Distance== | ||
Revision as of 16:46, 25 October 2010
Contents
Introduction and Advantages
Perspective and Background
Network discovery and routing table maintenance
The purpose of a routing protocol includes:
- Discovery of remote networks
- Maintaining up-to-date routing information
- Choosing the best path to destination networks
- Ability to find a new best path if the current path is no longer available
Advantages
Overview
|
Classifying Dynamic Routing Protocols
IGP and EGP
Distance Vector and Link State
Distance Vector bruger for det meste Bellman-Ford algoritmen.
Distance vector protocols work best in situations where:
- The network is simple and flat and does not require a special hierarchical design.
- The administrators do not have enough knowledge to configure and troubleshoot link-state protocols.
- Specific types of networks, such as hub-and-spoke networks, are being implemented.
- Worst-case convergence times in a network are not a concern.
Link-state protocols work best in situations where:
- The network design is hierarchical, usually occurring in large networks.
- The administrators have a good knowledge of the implemented link-state routing protocol.
- Fast convergence of the network is crucial.
Classful and Classless
Convergence
Metrics
Purpose of a Metric
Metrics and Routing Protocols
The metric for each routing protocol is:
- RIP: Hop count - Best path is chosen by the route with the lowest hop count.
- IGRP and EIGRP: Bandwidth, Delay, Reliability, and Load - Best path is chosen by the route with the smallest composite metric value calculated from these multiple parameters. By default, only bandwidth and delay are used.
- IS-IS and OSPF: Cost - Best path is chosen by the route with the lowest cost. . Cisco's implementation of OSPF uses bandwidth. IS-IS is discussed in CCNP.
Metric used in IP routing protocols:
- Hop count - A simple metric that counts the number of routers a packet must traverse
- Bandwidth - Influences path selection by preferring the path with the highest bandwidth
- Load - Considers the traffic utilization of a certain link
- Delay - Considers the time a packet takes to traverse a path
- Reliability - Assesses the probability of a link failure, calculated from the interface error count or previous link failures
- Cost - A value determined either by the IOS or by the network administrator to indicate preference for a route. Cost can represent a metric, a combination of metrics or a policy.
