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Network Devices

Common Network Devices

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Objectives

Install, configure and differentiate between common network devices

Network+2009 – Objective 3.1

What we will cover

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Hubs connect network segments together

Regenerate signals to increase the size of the network

Switches function at the Data-Link Layer (Layer-2)

Switch Symbol

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Bridges function at the Data-Link Layer (Layer-2)

Bridge Symbol

Routers operate at the Network layer (Layer-3)

Router Symbol

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Network Interface Cards (NIC) connect host to the network media

Wired

Wireless

Gateways can operate at any or all layers, they connect different network

types.

Netware Windows

MS Gateway Services for

Netware

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Wireless Access Point (WAP) provide wireless network connectivity

Modems convert digital signals to analog voice signals and vice-versa

Modem Modem

Analog Analog

Telco

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DSL Modems connects to Internet via PSTN copper pairs

DSL Modems use spare POTS bandwidth to carry Data

Cable Modems connects to Internet via cable network

Cable Modems use spare Cable Television (CATV) channels to carry Data

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Transceivers convert form one media type to another.

Gigabit Interface Converter (GBIC)

Small Form-Factor Pluggable (SFP)

Transceivers are also called Media Converters

Media converters(UTP to Fibre)

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Firewalls protect the network from outside threats.

Internal Network

(Trusted?)

Demilitarized Zone

Internet (Untrusted)

DHCP servers provide IP addresses and other network information

I need an IP Address

Okay, here is an IP

Address

ClientDHCP Server

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Summary

• Network interface adapters

• Hubs

• Bridges and switches

• Routers

• Firewalls

• Gateways

• Modems

• Wireless Access Point

• Transceivers

Physical Layer Devices

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The following are Physical Layer Devices

• Network Interface Card (NIC)

• Transceiver

• Repeater

• Hub

• MAU

• Modem

• Channel Service Unit/Data Service Unit (CSU/DSU)

Network Interface Cards connect the computer to the network media

Wireless

Wired

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Transceivers/Media Convertors convert from one media type to

another

Coaxial

AUI

FibreUTP

Media Attachment Unit (Ethernet)

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Repeaters regenerate network signals so they can travel for a greater distance

Repeaters are Physical layer devices that regenerate signals

Repeater

Extends Network Reach

SignalStrength

Maximum Segment Length

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Repeater

• Signals get weaker and more distorted the further from the source they get

• Repeaters regenerate the signals

Hubs are multi-port repeaters

Hubs connect multiple network segments together

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Hubs maintain a Single Collision and Broadcast Domain

Broadcast Domain

Collision Domain

RepeaterHub

Media Access Unit (Token Ring)

• Token Ring Media Access Unit (MAU, also called Multistation Access Unit, MSAU)

IBM 8228 (MAU)

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Dial-up Modem convert between digital signals and audio tones.

External Modem

Internal Modem

Modems convert digital signals to analog voice signals and vice-versa

Modem Modem

Analog Analog

Telco

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CSU/DSU interface your LAN to the Service Provider’s digital lines

CSU / DSU

Service Provider

Channel service unit / Data service unit

Your LAN

Channel Service Unit/Data Service Unit (CSU/DSU)

WAN Side LAN Side

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Summary

Network Interface Card (NIC)

Transceiver

Repeater

Hub

MAU

Modem

CSU/DSU

Data Link Layer Devices

Switches, Bridges, and Wireless Access Points

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Bridges and Switches connect multiple network segments at the data link

layer

Bridges and Switches

Are Data-link layer devices that use destination addresses to forward frames

Are Network protocol independent

Do not filter broadcast packets

Do not define separate networks

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Network without Bridge

Broadcast Domain

Collision Domain

RepeaterHub

Network with Bridge

Bridge

Broadcast Domain

Collision Domains

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Layer-2 Switches

Switch

Broadcast Domain

Collision Domains

Every interface on the Switch/Bridge is a separate Collision Domain

Collision

Domain

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Switches & Bridges have Three Main Functions

Address Learning

Forwarding/Filtering

Loop Avoidance

ADDRESS LEARNING

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Switch keeps a Table mapping MAC Address to Port

Port MAC Address

1

2

3

4

bbbb

1

2

3

4

aaaa

ddddcccc

MAC Address Table

Table is initially Empty

Switch learns the Address and Connected Port of Transmitting Device

Port MAC Address

1 aaaa

2

3

4

bbbb

1

2

3

4

aaaa

ddddcccc

MAC Address Table

I want to send to “cccc”

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Switch does not have destination address in it’s MAC table

Port MAC Address

1 aaaa

2

3

4

bbbb

1

2

3

4

aaaa

ddddcccc

MAC Address Table

I want to send to “cccc”

Switch Floods frame out of every port except the one it came in on.

Switch learns the Address and Connected Port of Transmitting Device

Port MAC Address

1 aaaa

2

3

4 cccc

bbbb

1

2

3

4

aaaa

ddddcccc

MAC Address Table

Switch learns the address of another device.

Reply to “aaaa”

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Switch finds Destination MAC address in its Table

Port MAC Address

1 aaaa

2

3

4 cccc

bbbb

1

2

3

4

aaaa

ddddcccc

MAC Address Table

Switch forwards the frame out ONLY the correct Port.

Reply to “aaaa”

Process continues until switch learns the Address and Port of all nodes

Port MAC Address

1 aaaa

2 dddd

3 bbbb

4 ccccbbbb

1

2

3

4

aaaa

ddddcccc

MAC Address Table

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Layer 2 Forwarding

Forwarding – device wants to send message to another device

bbbb

1

2

3

4

aaaa

dddd cccc

Port MAC Address

1 aaaa

2 dddd

3 bbbb

4 cccc

MAC Address Table

I want to send to “bbbb”

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Forwarding – switch looks for destination address in MAC Address

Table

bbbb

1

2

3

4

aaaa

dddd cccc

Port MAC Address

1 aaaa

2 dddd

3 bbbb

4 cccc

MAC Address Table

I want to send to “bbbb”

1. Lookup “bbbb” in MAC Table

2. Finds it

3. Forward Frame out ONLY the associated port

Layer 2 Switch Filtering

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Multiple Nodes on the Same Port

bbbb

13

4

aaaa

dddd

cccc

Hub

Port MAC Address

1 aaaa, dddd

2

3 bbbb

4 cccc

MAC Address Table

Frames destined out the same port they entered are dropped - Filtered

bbbb

13

4

aaaa

dddd

cccc

Hub

Port MAC Address

1 aaaa, dddd

2

3 bbbb

4 cccc

MAC Address Table

Sending to “dddd”

I don’t need to do anything

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Loop Avoidance

Networks with a “Single Point of Failure” are not as Reliable

Failure at any of these point will disrupt communication between clients and servers

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An additional Switch adds Redundancy

No more Single Point of Failure

However, Loops can now occur

Frames can now loop indefinitely around the network

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STP Blocks Layer-2 Loops even when Physical loops exists

Spanning Tree Protocol (STP) blocks some ports, to maintain a loop-free network

At what point of the frame does the switch start to forward the frame

Switches:

Cut-through

Store-and-forward

Bridges: Store-and-

forward

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Cut-through Switching

• The fastest way to forward frames

• Looks at only the first 6 bytes (destination MAC address) before forwarding

• No error checking

Rest of Frame

Forwarding Decision

Destination MAC Address

Fragment-free Switching

• Waits for the first 64 bytes before forwarding

• Catches most collisions

• Limited error checking

Rest of Frame

Forwarding Decision

Destination MAC Address

64

Bytes

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Store-and-Forward Switching

• Slower but more reliable than the cut-through

• Reads entire frame and performs a CRC check

• If CRC check fails – discard frame

Forwarding Decision

Complete Frame CRC

OTHER BRIDGING TECHNOLOGIES

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Source route bridging

• Used in Token Ring networks.

• The source node determines the path through the network, not the bridge.

• Bridges add path information when frames are forwarded

• Continue to use this information to forward frames between source and destination hosts.

Translation bridges are used to connect dissimilar data-link protocols.

Token Ring Ethernet

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Remote Bridges allow network segments to be connected over long

distances

Site A Site B

Wireless Access Points Bridge between Wireless and Wired devices

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Summary

• Why use Switches or Bridges

• Three functions of Switches and Bridges

• The Spanning Tree Protocol

• At what point to switch frames

• Other bridging technologies

Network Interface Cards

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A Network Interface Adapter

RJ-45 Jack PCI Connector

Diagnostic LEDs

Network Interface Card

• Links computer to the network

• Requires a device driver

• Plugs into an interface on a computer

• Network Interface Adapter

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Transmission Functions

• Data transfer, and buffering

• Data encapsulation

• Media Access Control (MAC)

• Parallel/serial conversion

• Signal encoding and amplification

Advanced NIC Features

Auto negotiation

Speed

10Mbps

100Mbps

1000Mbps

Duplex mode

Full duplex

Half duplex

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Advanced NIC Features (cont.)

Checksum processing

Processor offloading

Bus mastering

Transmission Control Protocol (TCP) segmentation

Internet Protocol Security (IPSec) processing

Network management

Wake on LAN

Selection Criteria

• Consider the following:

– The data-link layer protocol

– The transmission speed requirements

– Cabling and connector types

– Computer’s bus architecture and resource availability

– Network interface driver availability

– The operating system type

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Installing a NIC in a Computer

• To install a network interface adapter:

– Insert the NIC into the slot

– Configure the card to use the appropriate hardware resources

– Install the card’s device driver

Configuring a NIC

• For none plug and play (PnP) NICs, configure the following, as required:

– Interrupt request (IRQ)

– Input/output (I/O) port address

– Memory address

– Direct memory access (DMA) channel

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Device Drivers

• A device driver provides the link between operating system and the network interface adapter

OperatingSystem

DeviceDriver

NetworkCard

Configuration Tools

• Depends on the operating system

• For all Microsoft Windows operating systems, use the Device Manager utility

• Accessed from the System Properties dialog box in Control Panel or from the Computer Management console

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Configuration Tools (Continued)

• For Novell NetWare:

– Use Install.nlm for versions earlier than NetWare 5

– Use Nwconfig.nlm for NetWare 5

– Use Hdetect.nlm and Inetcfg.nlm for NetWare 6.5

• For UNIX or Linux, use the line command ifconfig

Isolating a Problem

Check existing cables and connectors are secure

Test with “known good” cables and connectors

Exclude other related hardware and software

Verify that the appropriate driver is installed

Verify that no conflicts exists with other devices

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Troubleshooting a Network Interface Card

Verify that the interface is seated properly in the bus slot

Remove the card, clean the connector, and test in the same slot or try another slot

Test with a known good card in the same slot and in a different slot

Network Layer Devices

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Routers

• Routers are network layer devices that connect networks

• Connect similar or different data-link layer LANs

• Must understand and support the network layer protocol and addressing

• Perform fragmentation

• Strip the data-link header and footer off received frames

Routers (Continued)

• Add a new data-link header and trailer before transmitting frames

• Use routing protocols to build routing tables and forward frames

• Define separate broadcast domains

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A Simple Routed Network

Switch

RouterSwitch

Network: 192.168.1.x Network: 192.168.2.x

Interface Address192.168.1.1

192.168.2.20

Interface Address192.168.2.254

192.168.1.20

A Routed Internetwork

Switch192.168.3.x

Switch192.168.2.x

Switch192.168.1.x

RouterA

RouterC

RouterB

2nd Floor

3rd Floor

1st Floor

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Layer-3 Switches

• Perform the same function as a Router

• Use special hardware integrated circuits

• ASIC – Application Specific Integrated Circuits

Routers & Layer-3 Switches come in all Sizes

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Gateways connect dissimilar systems and protocols

• Can include the functions of all seven layers of the Open Systems Interconnection (OSI) model

• Perform translation and conversion services

• Router were traditionally called Gateways

Netware Windows

MS Gateway Services for

Netware

Specialized Network Devices

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• At the end of this lesson we will be able to

– Identify the functions of specialized network devices

Network+2009 – Objective 3.2

What we will cover

• Multilayer switch• Content switch• IDS/IPS• Load balancer• Multifunction network devices• DNS server• Bandwidth shaper• Proxy server• CSU/DSU

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Multilayer switch operate at multiple layers of the OSI model

Cisco 6500 Series

Intrusion Detection System (IDS)

Internal (Protected) Network

External Network

IDS

Cisco IDS/IPS-4235

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Intrusion Prevention System (IPS)

External Network

Internal (Protected) NetworkIPS

Cisco IPS-4240

Load balancer distributes load across many servers

Servers

Minicomputer

Minicomputer

Minicomputer

MinicomputerLoad

Balancer

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Content switch optimize data delivery to clients

Minicomputer

Minicomputer

Minicomputer

Minicomputer

Content Switch

Multifunction network devices can provide more than one function

ISR

Integrated Services Router (ISR) –

Multifunction device

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Choose the Multifunction Device to suit your requirements

The Domain Name System (DNS) is a hierarchical naming system

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DNS servers resolve host name to IP address and vice versa

Minicomputer

DNSServer

What is the IP Address for?

Bandwidth Shaper or Traffic Shaper

Bandwidth

Shaper

Business Critical

Recreational

Business Critical

Non-Business Critical

Traffic IN Traffic OUT

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Proxy server

Minicomputer

ProxyServer Minicomputer

www.example.com

Makes request on behalf of client

Caches pages

Proxy returns previously cached pages

Channel Service Unit / Data Service Units

Provides the interface between your network and the service provider’s, for serial data

CSU/DSU

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Channel Service Unit / Data Service Units

To routerTo WAN circuit

Review

• Multilayer switch• Content switch• IDS/IPS• Load balancer• Multifunction network devices• DNS server• Bandwidth shaper• Proxy server• CSU/DSU