1. Simplified Networking
and Troubleshooting
for K-12 Teachers

2. 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+)

3. Example Client Site

4. 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
- 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

5. 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”

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

7. 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 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  

8. 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

9. Physical Layer (Ethernet)
The “Big Phone Plug”

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

11. More Ethernet Hardware

12. 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

13. 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
C-9C-B5
08:00:46:4C:9C:B5
0800:464C:9CB5

14. Common Ethernet Topologies

15. Limitations of Classical Ethernet
Distance limitations of UTP or Fiber
Network size limited by the 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 rule and just keep on adding hubs at random points

16. 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 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

17. 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

18. 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 :
IP addresses are written in dotted-decimal notation with the last number designating a particular computer***
Points to machine with
“street address” number 78
Points to the School’s “Zip Code”

19. IP Subnet Masking Network = 207.157.55 207.157.55.78 Host = 78
Network =
Host = 78
Network =
Host= 55.78

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

21. 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

22. Internet Settings

26. Static/DHCP Demonstration

27. 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:
(10/8 prefix)
(172.16/12 prefix)
( /16 prefix)

28. 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? (

29. Network Address Translation (NAT)

30. 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, , etc….

31. Proxy Server

32. Proxy Settings

35. 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
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”.
Host name (“Street Address”)
Domain Name (“Zip Code”)

36. DNS Tree

37. Routing 101

38. Traceroute – Tool of the Gods

39. Traceroute – no DNS (fast)

40. 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)

41. Interactive Command Review

42. 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).

43. 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
Step 6: if all of the above is fine ping and trace to
Step 7: if all of the above is fine ping and trace to
Step 8: if all of the above is fine ping and trace to

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

45. 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?

46. 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?

47. 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?

48. 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?