CCNA Explorer 2 Introduction to Routing and Packet Forwarding

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Introduction to Routing and Packet Forwarding

Inside the Router

Routers are Computers

1800 Router Front
1800 Router Back

Router CPU and Memory

1800 Router Inside. PSU,HWIC,HWIC,Fan,Ram,NVRAM,AIM,CPU from left to right, top to bottom
1841 Router.

Internetwork Operating System

Der findes forskellige IOS'er der har forskellige freatures.

Cisco IOS packaging framework

Router Boot-up Process

Router Boot-up process
Show version

Router interfaces

Interfaces. RJ45, Cisco Smart Serial Connector

PPP, Frame Relay, and HDLC (High-Level Data Link Control)

Logical Representation

Routers and the Network Layer

Packet Forwarding
Routing Process

CLI Configuration and Addressing

Basic Router Configuration

Basic Router config
Basic Router config 2

Building the Routing Table

Introducing the Routing Table

Routing Table

Vis en Route Print på windåse...

Static Routing

Static Routes

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

Dynamic Routing

Dynamic routing
Jobs of Dynamic Routing Protocols
  • Network Discovery
  • Maintaining Routing Tables

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

IP Packet Header
  • 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type of service - How the datagram should be handled (8 bits); the first 3 bits are precedence bits (this use has been superseded by Differentiated Services Code Point [DSCP], which uses the first 6 bits [last 2 reserved])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)
Ethernet Frame Header

Best Path and Metric

Hop Count vs Bandwidth

Equal Cost Load Balancing

Equal Cost Load Balancing

EIGRP - Unequal Cost Paths

Switching Function

A Day in the Life of a Packet