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Information Services

Working with Shared Folders and Printers in a Subnetted Environment

Computing Services Technote #535 v1

Title: Working with Shared Folders and Printers in a Subnetted Environment
Applies to: Campus users who share resources such as files and printers over the network
Section: Network Services
Author: Kevin Gates
Last updated: 23 March 2004

Introduction

One of the primary reasons for attaching computer systems to the campus LANis to allow sharing of information between computers.  While manymethods of doing this exist, one particularly popular method on our campus hasbeen "peer-to-peer" (P2P) sharing of resources.  P2P resourcesharing occurs when a computer on the network, typically a desktop systemlocated in someone's office, is configured to allow other users on the networkaccess to some or all of its resources.  Most commonly these resources arefiles and/or a shared printer.  Recent versions of major operating systems,including Microsoft Windows and Apple's MacOS, include features designed toallow users to easily share these resources with a minimum of hassle on smallcomputer networks.   However, changes to the configuration of ourcampus LAN will potentially make it more difficult for users to use theseintegrated OS file and print sharing features to exchange information withintheir department and with other colleagues.  The purpose of this documentis to discuss how these upcoming changes to our campus LAN will impact users whouser P2P resource sharing.

This document does not discuss the use of P2P file sharing programs such asKazaa, Grokster, Bearshare, Gnutella, Limewire, Morpheus, Napster, or Freewire. The use of such programs on campus computers is highly discouraged as they havea negative impact on our campus internet connection; they are the target ofnumerous computer viruses and worms; and, when configured incorrectly, pose asignificant security risk to both user and institutional data.

Network Configuration Change

For reliability and security reasons, Network Services has undertaken aproject to virtually modify how network traffic travels on campus.  Up until recently, our campus LAN was maintained as one single large entitywhere every system was able to talk directly to every other system on thenetwork.  In addition to being able to communicate directly with any othersystem on the network, it was possible for a system to broadcast a singlemessage to every other system on the network.  For example, when one computer needed to locate another it would broadcast amessage to every other machine on the network to find it.  The changes to our network will divide it into a numberof smaller virtual networks, called subnets.  Computers in each subnet will be able tocommunicate directly with each other and traffic between computers in differentsubnets will be routed between the subnets.

Our previous network design was not unlike a crowded gymnasium. Anyone in thegym can easily locate and communicate with anyone else in the gym. Announcement and general requests for information can also be made easily bysimply yelling out the information or question.  With our updated networkdesign we are taking the people out of the gym and dividing them up among anumber of smaller classrooms.  You can easily speak with anyone else in theclassroom and you can still make announcements and ask questions of the entireclassroom, but they are limited to the classroom you are in.  It is stillpossible to send information back and forth between classrooms but this istypically limited to a single target at the destination (for example, placing atelephone call to someone in the room).

Distribution of Subnets

The actual distribution of subnets will be based on the layout of thenetwork.  Every Ethernet cable located on campus runs back to a wiringcloset, cabinet, or utility room, usually located on or near the same floor ofthe building.  Each of these wiring closets has one or more stacks ofnetworking equipment mounted into a network frame.  Each network frame willreceive its own subnet.  Users can determine their network frame by lookingat the network drop ID number printed on the wall plate in their office. The first four characters identify your network frame.  For example, if yournetwork wall plate says "ED531/12" then your network frame is ED53 andyour computer will be located in the same subnet as all other computer pluggedinto wall plates starting with ED53.

Windows - File and Printer Sharing

Many campus users will be familiar with the "Network Neighbourhood"or "My Network Places" icon from their desktop.  Using theseicons, it was possible to graphically browse through a list of Windows basedcomputers located on the network and to access shared resources on these othercomputers.  When subnets are implemented, it will no longer be possible tobrowse through the lists of all available computers.  Here's why:

  • Every Windows based computer has a unique name and they are organized into workgroups.
  • When each computer starts up in the morning it broadcasts a message announcing its name and workgroup.  This is much like someone standing up in our gymnasium and yelling, "Hi! My name is Jim and I work for Computing Services."
  • The computers located on the network listen to the broadcasts and keep a list of workgroups and which computers are in the workgroups. This is something of a simplification of what really happens under the hood of your computer, but it is accurate enough for our discussion.
  • With our analogy, when we are all in the gymnasium, it is possible for us to listen to every person's announcement and get a complete list of everyone and what group they are in.
  • When we switch over to our classrooms, the walls will keep the announcements from traveling outside our our room.  So we will only know about the people and groups located in our own room.
  • With our new network design, the range of broadcasted messages will be limited to the subnet that they originate in. As such, the list of workgroups and computers will only contain those systems attached to the same network frame as you are currently located in.

For example:  Suppose that computers A and B are located on the 1stfloor of the Education building and computers C and D are located on the 5thfloor of the Education building and that they all belong to the "Smarties"workgroup.  When computer A browses the network neighbourhood it will seeitself and computer B.  When computer C browses the network neighbourhoodit will see itself and computer D.  Computer B will not automatically beable to browse to computer C or D etc, etc.

However, there is some good news.  Even if you can't browse to acomputer on the network using network neighbourhood, you can still access it.All you need to know is the name of the computer you are trying to access. Users who have previously placed an icon on their desktop or who have mapped anetwork drive to a shared Windows computer will still be able to use those iconsor mapped drives.  Users wishing to use resources on a computer they havenot previously accessed can do so as follows:

  • Click Start
  • Click Run
  • In the run dialog box type "\\computername" (without the quotes and with the real name of the target system instead of the word computername).  ex: \\softdist
  • click OK.
  • If you have spelled the name of the computer correctly and if you have security access to the shared resource, a window with a list of the shared resources on that computer will appear.
  • You can connect directly to a specific resource on a computer by typing "\\computername\resourcename" in the run dialog box.  Again, it is without the quotes, and the real computer and resource names should be substituted.  ex: \\softdist\pub
  • You can create create an icon on your desktop that leads directly to the resource.  Start by using the normal procedure to create a shortcut and then when prompted for a location, enter the "\\computername\resourcename" name.  Finish off the shortcut as you normally would.  Be warned though that desktop shortcuts to network resources will slow down your computer at boot time.

If you are sharing files with a colleague, you may need to tell them your computer nameso that they can connect to it. If you do not know your computer name, you can determineit as follows:

Under Windows 98:

  • Click START -> Click Settings -> Click Control Panel
  • When the control panel appears, double click the network icon.
  • A network window will appear. Click on the Identification tab.
  • The identification properties of your computer will appear and your computer name will be listed.
  • Click cancel to close the Network window and close the control panel.

Under Windows XP

  • Click Start -> Click Run.
  • In the run dialog box, type msinfo32 and click ok.
  • A system information window will appear. On the right hand side of the window, look for your system name.
  • Once you have located your system name, close the System Information window.

Printing to Network Attached Printers

Some systems on campus may be configured to print directly to a networkattached laser printer without the use of an intermediary server.  Quiteoften the IP address of the printer is hard coded into the computer system toallow communication.  However, under the new network design, the IPaddresses of printers will likely change.  Additionally, under the newsystem, the addresses are allocated dynamically and it is possible that evenafter the new design is implemented there are circumstances that could cause theprinter address to change again.  To minimize support problems, it would beadvantageous to configure computer systems to print to the domain name of theprinter rather than the IP address.  This can be done using the integratedprinting software that is included with Windows XP.  This cannot be doneusing older versions of the HP Jetdirect software that is used on many Windows98 systems.  Possible solutions to this issue include loading updatedsoftware that will accept domain names or allocating a special static IP addressfor the printer.  Allocating the static IP address may also be necessaryfor printing from Apple systems running older versions of MacOS.

Under Windows XP, the procedure to determine a system or printer's domain name is straightforward if you have the IP address.

  • Click Start -> Click Run
  • In the Run dialog box type CMD and click OK.
  • A command prompt window will appear.
  • In the command prompt window type nslookup XXX.XXX.XXX.XXX and press enter.You will need to substitute the correct IP address of the printer instead of the XXX.XXX.XXX.XXX.ex: nslookup 142.3.154.2
  • If a domain name exists for the IP address it will be displayed on your screen.
  • Type exit to close the command prompt window.

For assistance in determining domain names if you do not have Windows XP, please contact your departmental technician or the Computing Services IT Support Centre @ 4685.

MacOS

Apple users who configure their computer systems to use TCP/IP for accessingshared network resources should still be functional after the new network designis implemented.  In particular, MacOS X borrows heavily from the Unix worldfor its core functionality and should have little trouble with thetransition.  Users should be aware that when the switchover occurs, many IPaddresses will change.  Where possible, it would be advantageous to use thedomain name of the target system (ex: softdist.cc.uregina.ca) instead of the IPaddress (142.3.154.2) when setting up shares.  With MacOS, using Appletalkwill not allow you to access shares outside of your own network frame, so besure to enable the sharing via TCP/IP.

For additional help with Apple products please contact your departmentaltechnician or the IT Support Centre @4685.

Troubleshooting

If you are having difficulty using the file and print sharing features that areintegrated with your operating system, please contact your departmental computertechnician or the Computing Services IT Support Centre @ 4685.

Conclusion

Anticipated file and print sharing difficulties due to the subnetting of thecampus LAN are described.