Simplified Networking and Troubleshooting for K-12 Teachers

AREN Topology Multiple Star Network DS3/Partial OC-3 backbone Stars originate at the hub sites and hubs are connected by a North-South backbone DS3/Partial OC-3 backbone DS1 (T1) or Multiple T1 to clients Multiple Internet access points (DS3+)

Example Client Site

Network Related Services The following services are currently offered by AREN to all clients at low or no cost - High speed Internet access - DNS hosting and management - Web hosting and server management - Email hosting and server management - Expert network consulting (LAN and WAN) - Content filtering -CIPA “Technology Protection Measure” - Router management and site monitoring - In state Quality of Service (QoS) configuration

What is a Computer Network? Group of computers that are connected together and can communicate with each other in some way Connections can be serial, parallel, bus, radio, satellite, phone, etc. Can use Copper, Fiber-optics, Airwaves Can speak many different “protocols”

Component Review What are they and what are their uses? Computer NIC Printer Hub/Switch Router/CSU Proxy Server Email/Web Server

Simplified K12 Network Troubleshooting Day 1 (Theory and equipment) Introduction to Computer Networking (OSI) Review of Common Components (show and tell) Ethernet ins and outs (theory and hands-on) Intro to TCP/IP addressing (don’t worry!) DNS explained Day 2 (It’s broken, what do I do?) Quick review of Day 1 with any questions The Internet is down! My email doesn’t work! I can’t print! Where’s my network drive!?!? I can’t join this domain! Anything else y’all can throw at me  

OSI Reference Model Layer 1 – Physical Layer 2 – Data Link Hardware interface, electrical signaling, transmission of raw bit stream. Layer 2 – Data Link MAC (hardware) addressing, frame type, topology, switching Layer 3 – Network Logical addressing, IP is here, host to host communication Layer 4 - Transport End to end delivery guarantees, port addressing, stream delineation

Physical Layer (Ethernet) The “Big Phone Plug” http://www.rabcomputers.com/resources/cablepinout.htm http://www.aptcommunications.com/ncode.htm

Crimping Ethernet Cables Show and tell time No clip art available  Practice checking cables by sight

More Ethernet Hardware

Ethernet Types (Flavors) 10Base-2 (~200m, Coax) 10Base-5 (500m, Coax) 10Base-T (100m, Unshielded Twisted Pair = UTP) 10Base-FL (2000m=2km, Multimode Fiber) Fast Ethernet 100Base-TX (100m over CAT5 UTP) 100Base-FX (2000m=2km over MM Fiber) Gigabit Ethernet 1000Base-SX (300m over MM Fiber) 1000Base-LX (550m over MM Fiber, 3000m over SM Fiber) 10Gig

Ethernet: Classical (Data Link) 10 Mbps CSMA/CD Carrier Sense Multiple Access with Collision Detection Think CB radio (shared media, only used by one at a time) Can be configured with cable, hubs, or switches 1500 Byte Frames MAC addresses 08-00-46-4C-9C-B5 08:00:46:4C:9C:B5 0800:464C:9CB5

Common Ethernet Topologies

Limitations of Classical Ethernet Distance limitations of UTP or Fiber Network size limited by the 5-4-3 rule just remember hosts cannot talk to each other if they are connected through more than 4 hubs or repeaters One Broadcast Domain, One Collision Domain collisions likely as number of hosts increases Users generally don’t know about the 5-4-3 rule and just keep on adding hubs at random points

Ethernet: Current Baseline Layer 2 switches (Ethernet, FastE, GigE) Switching decisions are made based on MAC address Segments network into separate collision domains No more 5-4-3 rule Broadcasts are still heard by all hosts (1 bcast domain) Does not affect IP subnetting 802.1p provides QoS and is essential in Voice/IP or VTC implementations

TCP/IP Protocol Suite (don’t worry about remembering this now) IP = Internet Protocol Responsible for core rules: addressing, routing, packet size etc TCP = Transmission Control Protocol Responsible for creating point to point communication over the connectionless Internet UDP = User/Datagram Protocol Provides port address resolution

IP Addresses 207.157.55.78 Points to machine with Each computer also must have an IP address. This address is similar to the street address of a house in that each address is unique. Schools are assigned a group of IP addresses. This similar to a zip code for a street address. Example : 207.157.55.1 - 207.157.55.254 IP addresses are written in dotted-decimal notation with the last number designating a particular computer*** 207.157.55.78 Points to machine with “street address” number 78 Points to the School’s “Zip Code”

IP Subnet Masking Network = 207.157.55 207.157.55.78 Host = 78 255.255.255.0 255.255.0.0 Network = 207.157.55 Host = 78 Network = 207.157 Host= 55.78

Default Gateway The “Default Gateway” refers to the device that provides connectivity to (or towards) the rest of the world

Static vs. DHCP Static addressing DHCP addressing Each computer is “hard coded” with IP configuration. IP address never changes (Static) DHCP addressing Dynamic Host Configuration Protocol Computer automatically obtains IP address by sending broadcast query to the network

Internet Settings

Static/DHCP Demonstration

Private Addressing (RFC1918) Addresses that have no meaning to Internet routers These addresses are often used by school systems instead of public routable addresses Computer’s with these types of addresses must access the Internet through either proxy servers or translation devices From RFC1918: The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private internets: 10.0.0.0 - 10.255.255.255 (10/8 prefix) 172.16.0.0 - 172.31.255.255 (172.16/12 prefix) 192.168.0.0 - 192.168.255.255 (192.168/16 prefix)

Network Address Translation (NAT) RFC1918 addresses can be translated into routable public addresses PAT=Port address translation A single “real” address can be used to provide Internet access to thousands of computers using private addresses Exercise for the student: What is our “Real” address? (http://www.avl.lib.al.us/whatweknow.phtml)

Network Address Translation (NAT)

Proxy Server Instead of NAT Unlike NAT no address translation is used Client computer requests web page Proxy server retrieves web page and then passes page to client Protocols supported can be limited Some proxy servers only allow web access No telnet, ftp, chat, email, etc….

Proxy Server

Proxy Settings

DNS: Making English out of Numbers (DNS = Domain Name Service) IP addresses are hard to remember for humans, so IP names are much more useful. A computers IP address can be associated with an IP name. IP Names use a dotted notation, for example www.foxnews.com Using the same address analogy, the Linden k12 network has been assigned a domain name (“zip code”) of linden.k12.al.us. All computers are also given a host names that are the “street addresses”. www.linden.k12.al.us Host name (“Street Address”) Domain Name (“Zip Code”)

DNS Tree

Routing 101

Traceroute – Tool of the Gods

Traceroute – no DNS (fast)

Troubleshooting at last! Commands you must know and love: ping (the daddy of them all) traceroute (tracert in Microsoft land) ipconfig (ipconfig /all for details) ipconfig /release (ipconfig /renew) winipcfg (for Win95) nslookup (not available in Win9x)

Interactive Command Review

The Internet is Down ! This is a very generic statement and generally means that folks can’t get to web sites with their browser (Internet Explorer and/or Netscape).

The Internet is Down ! Step 1: Check link light and Ethernet cable - if no link check cable - check hub/switch lights and power Step 2: Confirm IP is configured on host and address is valid - check with ipconfig (or winipcfg) Step 3: Ping Default Gateway - find Gateway using ipconfig (or winipcfg) Step 4: Ping school proxy server and/or NAT device Step 5: if all of the above is fine ping and trace to 129.66.12.151 Step 6: if all of the above is fine ping and trace to www.asc.edu Step 7: if all of the above is fine ping and trace to 149.149.11.7 Step 8: if all of the above is fine ping and trace to www.tntech.edu

My Email Doesn’t work ! Step 1: Confirm that you have access to other Network resources (web, ftp, telnet, etc.) Step 2: Check email server configuration in email client (method varies by client) Step 3: Can you receive email from outside school system? Step 4: Can you receive email from inside school system? Step 5: Can you send email to addresses outside system? Step 6: Can you send email to addresses inside system?

I Can’t print! (Network Printer) Is the printer “online”? Confirm that you have access to other Network resources (web, ftp, telnet, etc.) If IP address of printer or print server is known, try to ping it. If printer attached to a computer, can you print from that computer?

I Can’t print! (Local Printer) Is the printer “online”? Is the printer out of paper? Ink? What message(s) are you getting from the driver? Is the local driver software still installed?

Step 4: Can you ping the share name? Can’t “see” anything in Network Neighborhood (no access to network shares) Step 1: Confirm that you have access to other Network resources (web, ftp, telnet, etc.) Step 2: Did you authenticate into the local domain (hitting cancel at login is not a good idea) Step 3:Is the share reached via Network Neighborhood or a pre-mapped drive letter? Step 4: Can you ping the share name? Step 5: Can you ping the IP address of the file server?

I can’t get this “&*#ing” computer to join the domain! New Computer: 1) You must be an administrator to add a computer to a domain. Existing Computer that worked previously: 1) Confirm that you have access to other Network Resources (web, ftp, telnet, etc.) 2) Do you have a valid domain username/password?