Internet Connection Internet Connection SharingSharing

Ben RamigBen Ramig

Erik TierneyErik Tierney

Internet Connection Internet Connection SharingSharing

What is it?What is it?• Solution for sharing a single internet Solution for sharing a single internet

connection with multiple computers connection with multiple computers attached to a Local Area Network (LAN)attached to a Local Area Network (LAN)

• Recommended for private home Recommended for private home networksnetworks

Why?Why?• Cut costsCut costs

Home Networking Home Networking SolutionsSolutions

AdvantagesAdvantages• Multiple computers Multiple computers

can share single can share single Internet ConnectionInternet Connection

• Cuts ISP CostsCuts ISP Costs– Comcast charges Comcast charges

$7/month for each $7/month for each additional IP address additional IP address and only allows a and only allows a total of 3 addressestotal of 3 addresses

DisadvantagesDisadvantages• Limits access from Limits access from

the internet to the internet to only the host only the host machine (firewall)machine (firewall)

• Some winsock Some winsock program features program features may not work may not work properly or require properly or require special settingsspecial settings

Home Networking Home Networking SolutionsSolutions

WindowsWindows• Wingate Internet Sharing Software ($40 Wingate Internet Sharing Software ($40

for 3-user license, $70 for 6-user license)for 3-user license, $70 for 6-user license)• Internet Connection Sharing Wizard Internet Connection Sharing Wizard

(included with Windows 98 Second (included with Windows 98 Second Edition)Edition)

LinuxLinux• IP Firewall Chains IP Firewall Chains

– IP MasqueradingIP Masquerading

IP Masquerading IP Masquerading FundamentalsFundamentals

Gateway rewrites packets so that Gateway rewrites packets so that they appear to have originated they appear to have originated from it (instead of a computer on from it (instead of a computer on the internal network)the internal network)

Rewrites responses as well and Rewrites responses as well and routes them to the internal routes them to the internal computer that made the request.computer that made the request.

Internet Service Provider Internet Service Provider TypesTypes

Modem - 56k (Free to $20/month)Modem - 56k (Free to $20/month)

Cable - 10Mb/s - security issues Cable - 10Mb/s - security issues ($40 - $55/month)($40 - $55/month)

DSL - 10Mb/s - ($50/month)DSL - 10Mb/s - ($50/month)

Hardware RequiredHardware Required

Cable, DSL, or Analog ModemCable, DSL, or Analog Modem

Network Interface CardsNetwork Interface Cards• One for each client, two for host machineOne for each client, two for host machine

Hub and CAT5 Ethernet CablesHub and CAT5 Ethernet Cables• Uplink capability vs. No UplinkUplink capability vs. No Uplink

– Can get away with using only one network card in host Can get away with using only one network card in host machine if not using Microsoft Internet Connection machine if not using Microsoft Internet Connection Sharing WizardSharing Wizard

– 8 port uplink hub goes for about $258 port uplink hub goes for about $25

Network OverviewNetwork Overview

ISP Provider – Static/Dynamic IP AddressISP Provider – Static/Dynamic IP Address• Ex: 24.7.X.XEx: 24.7.X.X

Local Area Network – Internal IP Local Area Network – Internal IP AddressesAddresses• Ex: 192.168.X.XEx: 192.168.X.X

Host machine is usually 192.168.0.1 Host machine is usually 192.168.0.1 since it is the gateway between LAN and since it is the gateway between LAN and InternetInternet

Microsoft ICS WizardMicrosoft ICS Wizard

AdvantagesAdvantages• No additional cost No additional cost

for licensesfor licenses

• Part of the new Part of the new Windows Windows operating systemoperating system

DisadvantagesDisadvantages• Requires Windows Requires Windows

98SE or Windows 98SE or Windows 20002000

• All client machines All client machines must be running must be running WindowsWindows

• Not very user Not very user friendlyfriendly

ICS Host Machine Setup – ICS Host Machine Setup – Part 1Part 1

Internet connection must be setup Internet connection must be setup properly (usually done by Internet properly (usually done by Internet Service Provider)Service Provider)

Must be running Win98SE or Win2000Must be running Win98SE or Win2000

Install ICS Component under Window Install ICS Component under Window Setup option in the control panelSetup option in the control panel

Starting Microsoft ICS Starting Microsoft ICS Wizard Wizard

Selecting Connection TypeSelecting Connection Type

ICS Host Machine Setup – ICS Host Machine Setup – Part 2Part 2

Choose type of internet connectionChoose type of internet connection• Fast (Cable/DSL/etc), Slow (Modem)Fast (Cable/DSL/etc), Slow (Modem)

Tell ICS Wizard which adapter is for Tell ICS Wizard which adapter is for Internet and which is for LANInternet and which is for LAN

Restart computer and all clientsRestart computer and all clients

Binding Network AdaptersBinding Network Adapters

Client Configuration DiskClient Configuration Disk

ICS Network AdapterICS Network Adapter

Internet Sharing ProtocolsInternet Sharing Protocols

Windows 2000 ICS SetupWindows 2000 ICS Setup

ICS Client Machine SetupICS Client Machine Setup

Must be running Windows Must be running Windows 95/98/NT/200095/98/NT/2000

Do NOT install NetBEUI protocol on any Do NOT install NetBEUI protocol on any of the client machines!of the client machines!

TCP/IP Configuration:TCP/IP Configuration:• DHCP for WINS Resolution and IP DHCP for WINS Resolution and IP

ConfigurationConfiguration• Remove all gateways (if any are present)Remove all gateways (if any are present)• Disable DNS ConfigurationDisable DNS Configuration

Linux vs. Windows for HostLinux vs. Windows for Host

LinuxLinux• Real Network OSReal Network OS• Cheap 486 with Cheap 486 with

just network card just network card can be usedcan be used

• Better security Better security and stabilityand stability

• Much more Much more flexibility with IP flexibility with IP ChainsChains

WindowsWindows• Easier to setupEasier to setup• Most people Most people

already know the already know the system and are system and are familiar with itfamiliar with it

Linux IP ChainsLinux IP Chains

Consists of rules and policies for Consists of rules and policies for packet filtering and IP packet filtering and IP masquerading masquerading

3 Chains3 Chains• Input chainInput chain• Forwarding ChainForwarding Chain• Output chainOutput chain