View source for CCNA Explorer 2 Introduction to Routing and Packet Forwarding

=Introduction to Routing and Packet Forwarding=
==Inside the Router==
===Routers are Computers===
{|
|[[Image:ScreenShot698.jpg|800px|left|thumb|1800 Router Front]]
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|[[Image:ScreenShot697.jpg|800px|left|thumb|1800 Router Back]]
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===Router CPU and Memory===
{|
|[[Image:ScreenShot699.jpg|800px|left|thumb|1800 Router Inside. PSU,HWIC,HWIC,Fan,Ram,NVRAM,AIM,CPU from left to right, top to bottom]]
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|[[Image:ScreenShot700.jpg|800px|left|thumb|1841 Router.]]
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===Internetwork Operating System===
Der findes forskellige IOS'er der har forskellige freatures.
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|[[Image:ScreenShot701.jpg|800px|left|thumb|Cisco IOS packaging framework]]
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http://www.cisco.com/en/US/prod/collateral/iosswrel/ps8802/ps10587/ps10591/ps10621/qa_c67_561940.html
===Router Boot-up Process===
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|[[Image:ScreenShot702.jpg|800px|left|thumb|Router Boot-up process]]
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|[[Image:ScreenShot703.jpg|800px|left|thumb|Show version]]
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===Router interfaces===
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|[[Image:ScreenShot704.jpg|800px|left|thumb|Interfaces. RJ45, Cisco Smart Serial Connector]]<br/>
PPP, Frame Relay, and HDLC (High-Level Data Link Control)
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|[[Image:ScreenShot705.jpg|800px|left|thumb|Logical Representation]]
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===Routers and the Network Layer===
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|[[Image:ScreenShot706.jpg|800px|left|thumb|Packet Forwarding]]
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|[[Image:ScreenShot707.jpg|800px|left|thumb|Routing Process]]
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==CLI Configuration and Addressing==
===Basic Router Configuration===
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|[[Image:ScreenShot708.jpg|800px|left|thumb|Basic Router config]]
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|[[Image:ScreenShot709.jpg|800px|left|thumb|Basic Router config 2]]
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==Building the Routing Table==
===Introducing the Routing Table===
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|[[Image:ScreenShot710.jpg|800px|left|thumb|Topology]]
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|[[Image:ScreenShot711.jpg|800px|left|thumb|Routing Table]]
Vis en '''Route Print''' på windåse...
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===Static Routing===
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|[[Image:ScreenShot712.jpg|800px|left|thumb|Static Routes]]
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'''Use Static routes when:'''
*A network consists of only a few routers
*A network is connected to the Internet only through a single ISP
*A large network is configured in a hub-and-spoke topology
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===Dynamic Routing===
{|
|[[Image:ScreenShot713.jpg|800px|left|thumb|Dynamic routing]]
|-
|'''Jobs of Dynamic Routing Protocols'''
*Network Discovery
*Maintaining Routing Tables
<br/><br/>
'''IP Routing Protocols'''
*RIP (Routing Information Protocol) 
*IGRP (Interior Gateway Routing Protocol)
*EIGRP (Enhanced Interior Gateway Routing Protocol)
*OSPF (Open Shortest Path First)
*IS-IS (Intermediate System-to-Intermediate System)
*BGP (Border Gateway Protocol)
|}
==Path Determination and Switching Functions==
===Packet Fields and Frame Fields===
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|[[Image:ScreenShot714.jpg|800px|left|thumb|IP Packet Header]]
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*'''Version''' - Version number (4 bits); predominant version is IP version 4 (IPv4)
*'''IP header length''' - Header length in 32-bit words (4 bits)
*'''Precedence and type of service''' - How the datagram should be handled (8 bits); the first 3 bits are precedence bits (this use has been superseded by Differentiated Services Code Point [DSCP], which uses the first 6 bits [last 2 reserved])
*'''Packet length''' - Total length (header + data) (16 bits)
*'''Identification''' - Unique IP datagram value (16 bits)
*'''Flags''' - Controls fragmenting (3 bits)
*'''Fragment offset''' - Supports fragmentation of datagrams to allow differing maximum transmission units (MTUs) in the Internet (13 bits)
*'''Time to Live (TTL)''' - Identifies how many routers can be traversed by the datagram before being dropped (8 bits)
*'''Protocol''' - Upper-layer protocol sending the datagram (8 bits)
*'''Header checksum''' - Integrity check on the header (16 bits)
*'''Source IP address''' - 32-bit source IP address (32 bits)
*'''Destination IP address''' - 32-bit destination IP address (32 bits)
*'''IP options''' - Network testing, debugging, security, and others (0 or 32 bits, if any)
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|[[Image:ScreenShot715.jpg|800px|left|thumb|Ethernet Frame Header]]
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===Best Path and Metric===
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|[[Image:ScreenShot716.jpg|800px|left|thumb|Hop Count vs Bandwidth]]
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===Equal Cost Load Balancing===
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|[[Image:ScreenShot717.jpg|800px|left|thumb|Equal Cost Load Balancing]]
EIGRP - Unequal Cost Paths
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===Switching Function===
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|[[Image:ScreenShot719.jpg|800px|left|thumb|A Day in the Life of a Packet]]
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==Summary==
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|[[Image:ScreenShot720.jpg|800px|left|thumb|Summary]]
|}