Internet Connection Sharing Ben Ramig Erik Tierney

Internet Connection Sharing b What is it? Solution for sharing a single internet connection with multiple computers attached to a Local Area Network (LAN)Solution for sharing a single internet connection with multiple computers attached to a Local Area Network (LAN) Recommended for private home networksRecommended for private home networks b Why? Cut costsCut costs

Home Networking Solutions b Advantages Multiple computers can share single Internet ConnectionMultiple computers can share single Internet Connection Cuts ISP CostsCuts ISP Costs –Comcast charges $7/month for each additional IP address and only allows a total of 3 addresses b Disadvantages Limits access from the internet to only the host machine (firewall) Some winsock program features may not work properly or require special settings

Home Networking Solutions b Windows Wingate Internet Sharing Software ($40 for 3- user license, $70 for 6-user license)Wingate Internet Sharing Software ($40 for 3- user license, $70 for 6-user license) Internet Connection Sharing Wizard (included with Windows 98 Second Edition)Internet Connection Sharing Wizard (included with Windows 98 Second Edition) b Linux IP Firewall ChainsIP Firewall Chains –IP Masquerading

IP Masquerading Fundamentals b Gateway rewrites packets so that they appear to have originated from it (instead of a computer on the internal network) b Rewrites responses as well and routes them to the internal computer that made the request.

Internet Service Provider Types b Modem - 56k (Free to $20/month) b Cable - 10Mb/s - security issues ($40 - $55/month) b DSL - 10Mb/s - ($50/month)

Hardware Required b Cable, DSL, or Analog Modem b Network Interface Cards One for each client, two for host machineOne for each client, two for host machine b Hub and CAT5 Ethernet Cables Uplink capability vs. No UplinkUplink capability vs. No Uplink –Can get away with using only one network card in host machine if not using Microsoft Internet Connection Sharing Wizard –8 port uplink hub goes for about $25

Network Overview b ISP Provider – Static/Dynamic IP Address Ex: 24.7.X.XEx: 24.7.X.X b Local Area Network – Internal IP Addresses Ex: X.XEx: X.X b Host machine is usually since it is the gateway between LAN and Internet

Microsoft ICS Wizard b Advantages No additional cost for licensesNo additional cost for licenses Part of the new Windows operating systemPart of the new Windows operating system b Disadvantages Requires Windows 98SE or Windows 2000 All client machines must be running Windows Not very user friendly

ICS Host Machine Setup – Part 1 b Internet connection must be setup properly (usually done by Internet Service Provider) b Must be running Win98SE or Win2000 b Install ICS Component under Window Setup option in the control panel

Starting Microsoft ICS Wizard

Selecting Connection Type

ICS Host Machine Setup – Part 2 b Choose type of internet connection Fast (Cable/DSL/etc), Slow (Modem)Fast (Cable/DSL/etc), Slow (Modem) b Tell ICS Wizard which adapter is for Internet and which is for LAN b Restart computer and all clients

Binding Network Adapters

Client Configuration Disk

ICS Network Adapter

Internet Sharing Protocols

Windows 2000 ICS Setup

ICS Client Machine Setup b Must be running Windows 95/98/NT/2000 b Do NOT install NetBEUI protocol on any of the client machines! b TCP/IP Configuration: DHCP for WINS Resolution and IP ConfigurationDHCP for WINS Resolution and IP Configuration Remove all gateways (if any are present)Remove all gateways (if any are present) Disable DNS ConfigurationDisable DNS Configuration

Linux vs. Windows for Host b Linux Real Network OSReal Network OS Cheap 486 with just network card can be usedCheap 486 with just network card can be used Better security and stabilityBetter security and stability Much more flexibility with IP ChainsMuch more flexibility with IP Chains b Windows Easier to setup Most people already know the system and are familiar with it

Linux IP Chains b Consists of rules and policies for packet filtering and IP masquerading b 3 Chains Input chainInput chain Forwarding ChainForwarding Chain Output chainOutput chain