IB 300 Advanced Computer Sciences Professor Nabil Elmjati Ethernet Troubleshooting What does network does not work mean Internet down Server down One computer or group of computers cant access network ID: 300083
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Network Troubleshooting
IB 300: Advanced ComputerSciences.Professor: Nabil ElmjatiSlide2
Ethernet Troubleshooting
What does “network does not work” mean?Internet downServer downOne computer, or group of computers can’t access networkWing of building downWhole building downUnderstand the “path” data takes through the networkWhat does work, and specifically, what does notSlide3Slide4
Common problems
Four common network problem categories:Everything is slow/not workingInternet is slow, server access is normalServer access is slow/not working, Internet access seems normalSingle computer, room of computers, area of building is slow/not working Slide5
Everything is slow/not working
Wiring/Network problemsEthernet loopsTwo wires to wall? (use ONE red cable)Use colored cables if possible.Count cables/computersRemove extra cablesSlide6Slide7Slide8
Everything is slow/not working (cont.)
Wiring/Network problems (cont.)Cable too long (more than 97m)Cable not well pressed, causing timeouts?Slide9
Everything is slow/not working (cont.)
Network is very busy, so it’s slow (solid activity lights on switches) Look at lights on switches, unplug-replug one at a time to see if traffic returns to normal - note the port and track it downCauses:Worm viruses/spywareLoop“Chattery Network Card” (bad drivers or bad card)
Keep OS updates and anti-Virus software up to dateSlide10
Internet is slow/not working (cont.)
Can be a Router ProblemTurn router off and back onCan be a “Upstream” problemPing aroundSlide11
What is Ping
Ping is a computer network administration utility used to test the reach ability of a host on an Internet Protocol (IP) network and to measure the round-trip time for messages sent from the originating host to a network card on a destination computer. The name comes from active sonar terminology which sends a pulse of sound and listens for the echo to detect objects underwater. With computer operating systems Ping or PING stands for Packet INternet Groper but is ordinarily written as "ping" instead of the proper acronym for which it stands.Slide12
Ping around
Get to a command promptXP/Win2k/VistaRun “ipconfig”Note your default gatewayRun “Ping <default gateway>”No response, your router may not be workingRun “Ping <known district server/router>No response, your connection to the outside world (Geomax/T1 etc) is down
Run “ping www.google.com”No response - your district’s connection to the outside world is downSlide13
Internet is slow/not working
Overloaded Wan line(s)Can be worm/e-mail viruses eating up bandwidthCan be peer-to-peer file sharing program on a computer in your schoolStreaming video/audio congesting the network? Slide14
Server is slow/not working
What you *CAN* doStep 1Un-plug/re-plug the server’s network cablesFirst Contact helpdesk/your NA.Don’t move them, plug them back in the same placeOnly do one end of one cable at a time
The server will be “down” while they are un-pluggedStep 2 (still not working)
Check it out, or have the network guy check it out
Contact helpdesk/your NE
, get server restartedSlide15
Group of computers is slow/not working
What do they have in common?All connected to same switch?Power-cycle switchCheck for loopsChange portReplace switchSlide16
Group of computers is slow/not working (cont.)
What do they have in common? (cont.)All same model/from same image?Virus/Spyware in image?Client software installed/configured wrong?OS not patched?Bad NIC driver?Same “wing” or areaPower cycle switchesSlide17
Single computer is slow/not working
Restart the computerUn-plug/re-plug/replace cablesCheck it’s connection at Switch or hubSlide18
Single computer is slow/not working (cont.)
Change it’s portDon’t move other wiresDon’t “clean up” wiring!!!If it doesn't fix it, change it backPatches/ AntiVirus / SpywareUpgrade/Re-install NIC driverReplace NICForce speed/duplex (gig switch, Cat5 wiring?)Slide19
Troubleshooting Internet at home
Before trying to fix any issue regarding you home network or internet you will need to understand how the network is set up in your house.Slide20Slide21
Internet not Working!
First: Check if your computer has an IP addressIf you don’t have an ip, check if your NIC is properly working.Second: Ping your router.If there is no response power cycle your routerThird: Plug-in directly to your router (turn off Wifi) or check another computer on your network, to see if you are the only one affected.Fourth: Log in to your router to see if you are connected to your ISP. If not check your setting or call your ISPSlide22
Internet is slow!
Important: Always ask yourself before starting your troubleshooting: is your network secure?First: Reboot your Router. See if that fixes it.Second: Check if someone on your network is using filesharing softwares or video streaming. Third: Ping your router to check the latency as well as an IP address and hostname for a known site like google.
If latency is smaller when you ping the ip address of a host, then your ISP has a DNS issue.
Fourth: Log in to your router
to see if your line has the ordered Speed from your ISP