Introduction to networking

Devices

Objectives Be able to describe the common networking

devices and their functionality, including: Repeaters Hubs Switches Bridges Routers

Icons

Repeater This receives a signal from the network and then

repeats it After a distance an electrical signal will lose power

(attenuation) This node increases the power of the signal again

Hub Multi-port repeater Shares bandwidth Prone to collisions Uses the Ethernet CSMACD technique to

govern communication Cheap Generally non-configurable

Switch Based on the Ethernet MAC address this node will

forward the data to the correct host/machine Creates micro-segments Avoids the CSMACD issues of collision Bandwidth is not divided between connected

hosts Provides Virtual LAN’s Can be very basic and very advanced Advanced models highly configurable

Bridge Connects two segments of a network together Only allows data to pass if the destination

host/machine is located on the other segment Preserves bandwidth

Routers Similar to a bridge Based on the IP Address this node will forward the data

to the correct host/machine Calculates the ‘best path’ Also performs a switching function Uses routing tables Convergence Uses routing protocols Uses ACL’s (Access Control Lists) for security ‘Knows’ the network Can be very advanced, highly configurable

Routers Internal components

D/RAM: storing routing tables, ARP cache, temporary and running memory for the config file Loses data when powered down

NVRAM: stores backup/startup config file Flash: EPROM, hold OS image, allows OS to be

updated, can contain multiple OS’s ROM: POST, bootstrap and basic OS Interface: where packets enter and exit router

Routers Routers can operate at all 7 levels of OSI, but

mainly at levels 1-3 Communication via level 1 and 2 refer to the

routers switching function Routes identify routes via layer 3 Routers are quite simple physically, but very

complicated logically due to its routing logic

Router internal components

You will mostly experience the I/O interfaces and the IOS(the configuration file)

Router functions One physical path must exist between source

and destination Having and using a path are not the same

thing! Source and destination must speak the same

language (routed protocol), routers should also speak the same language (routing protocol), and agree on path

Functions therefore are: Physical interconnectivity Logical interconnectivity Route calculation and maintenance security

Internal components of a 2600 router

Router external connections (2600)WAN interfaces

LAN interfacesManagement ports

WAN connections provide connections through a serviceProvider to a distant site or the Internet, often a CSU/DSU isrequired

Management ports Text based CLI configuration and

troubleshooting Console and auxiliary are used for this (EIA-

232 asynchronous serial ports) Console is the preferred method of configuring

as an administrator has access to router despite what state it is in and it allows the administrator to see and start-up messages

Terminal console connection

HyperTerminal settings

Summary The main devices you will use are:

Switches Routers Hosts Relevant cabling

Cisco Switches and Routers for the CCNA are very advanced and highly configurable

Questions... ...are there any?