Download AREN - ASC

09999/2106
Simplified Networking
and Troubleshooting
for K-12 Teachers
AREN Topology
09999/2106
• Multiple Star Network
– 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
09999/2106
AREN
CSU/DSU
CISCO SYSTEMS
CISCO SYSTEMS
Server
Computer
Computer
Computer
Network Related Services
09999/2106
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?
09999/2106
• 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
09999/2106
What are they and what are their uses?
•
•
•
•
•
•
•
Computer
NIC
Printer
Hub/Switch
Router/CSU
Proxy Server
Email/Web Server
Simplified K12 Network Troubleshooting
09999/2106
• 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
09999/2106
• Layer 1 – Physical
– 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)
09999/2106
• The “Big Phone Plug”
• http://www.rabcomputers.com/resources/cablepinout.htm
• http://www.aptcommunications.com/ncode.htm
Crimping Ethernet Cables
09999/2106
• Show and tell time
• No clip art available 
• Practice checking cables by sight
More Ethernet Hardware
09999/2106
Workstation
Workstation
Workstation
Ethernet Types (Flavors)
09999/2106
• Ethernet
–
–
–
–
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)
09999/2106
• 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
09999/2106
Hub
IBM Compatible
IBM Compatible
Server
Ethernet
Hub
Hub
Workstation
ComputerComputer
Computer Computer
Stackable Hubs
Computer
Computer
Computer
Computer
Computer
Computer
Mac II
Limitations of Classical Ethernet
09999/2106
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
09999/2106
• 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
Ethernet Switch
Ethernet Hub
129.66.32.4
129.66.32.3
129.66.32.1129.66.32.2
TCP/IP Protocol Suite
(don’t worry about remembering this now)
09999/2106
• 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
09999/2106
• 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 the School’s “Zip Code”
Points to machine with
“street address” number 78
IP Subnet Masking
09999/2106
207.157.55.78
Network = 207.157.55
255.255.255.0
Host = 78
207.157.55.78
Network = 207.157
255.255.0.0
Host= 55.78
Default Gateway
09999/2106
The “Default Gateway”
refers to the device that
provides connectivity to
(or towards) the rest of
the world
AREN
CSU/DSU
CISCO SYSTEMS
CISCO SYSTEMS
Server
Computer
Computer
Computer
Static vs. DHCP
09999/2106
• Static 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
09999/2106
09999/2106
09999/2106
09999/2106
Static/DHCP Demonstration
09999/2106
Private Addressing (RFC1918)
09999/2106
• 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)
09999/2106
• 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)
09999/2106
10.10.10.2
Internet
Private Network
With RFC1918 addresses
10.10.10.3
10.10.10.4
10.10.10.1
and
207.157.78.50
Proxy Server Instead of NAT
09999/2106
• 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
09999/2106
10.10.10.2
Internet
Private Network
With RFC1918 addresses
10.10.10.3
Outside address: 207.157.87.3
Inside address 10.10.10.1
10.10.10.4
Proxy Settings
09999/2106
09999/2106
09999/2106
DNS: Making English out of Numbers
(DNS = Domain Name Service)
09999/2106
• 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
1) Linden.k12.al.us ?
09999/2106
us root
al.us server
Workstation
k12.al.us server
linden.k12.al.us server
Local DNS server
Routing 101
09999/2106
The Internet
LAN
Router
Router
LAN
Router
Router
LAN
LAN
Traceroute – Tool of the Gods
09999/2106
Traceroute – no DNS (fast)
09999/2106
Troubleshooting at last!
09999/2106
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
09999/2106
The Internet is Down !
09999/2106
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 !
09999/2106
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 !
09999/2106
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)
09999/2106
1) Is the printer “online”?
2) Confirm that you have access to other
Network resources (web, ftp, telnet, etc.)
3) If IP address of printer or print server is
known, try to ping it.
4) If printer attached to a computer, can you
print from that computer?
I Can’t print! (Local Printer)
09999/2106
1) Is the printer “online”?
2) Is the printer out of paper? Ink?
3) What message(s) are you getting from the
driver?
4) Is the local driver software still installed?
Can’t “see” anything in Network Neighborhood
(no access to network shares)
09999/2106
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!
09999/2106
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?