IB 300: Advanced Computer Sciences. Professor: Nabil Elmjati

 What does “network does not work” mean?  Internet down  Server down  One computer, or group of computers can’t access network  Wing of building down  Whole building down  Understand the “path” data takes through the network  What does work, and specifically, what does not

 Four common network problem categories: 1. Everything is slow/not working 2. Internet is slow, server access is normal 3. Server access is slow/not working, Internet access seems normal 4. Single computer, room of computers, area of building is slow/not working

 Wiring/Network problems  Ethernet loops  Two wires to wall? (use ONE red cable)  Use colored cables if possible.  Count cables/computers  Remove extra cables

 Wiring/Network problems (cont.)  Cable too long (more than 97m)  Cable not well pressed, causing timeouts?

 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 down  Causes:  Worm viruses/spyware  Loop  “Chattery Network Card” (bad drivers or bad card)  Keep OS updates and anti-Virus software up to date

 Can be a Router Problem  Turn router off and back on  Can be a “Upstream” problem  Ping around

 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.

 Get to a command prompt  XP/Win2k/Vista  Run “ipconfig”  Note your default gateway  Run “Ping ”  No response, your router may not be working  Run “Ping  No response, your connection to the outside world (Geomax/T1 etc) is down  Run “ping  No response - your district’s connection to the outside world is down

 Overloaded Wan line(s)  Can be worm/ viruses eating up bandwidth  Can be peer-to-peer file sharing program on a computer in your school  Streaming video/audio congesting the network?

 What you *CAN* do  Step 1  Un-plug/re-plug the server’s network cables  First Contact helpdesk/your NA.  Don’t move them, plug them back in the same place  Only do one end of one cable at a time  The server will be “down” while they are un-plugged  Step 2 (still not working)  Check it out, or have the network guy check it out  Contact helpdesk/your NE, get server restarted

 What do they have in common?  All connected to same switch?  Power-cycle switch  Check for loops  Change port  Replace switch

 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 area  Power cycle switches

 Restart the computer  Un-plug/re-plug/replace cables  Check it’s connection at Switch or hub

 Change it’s port  Don’t move other wires  Don’t “clean up” wiring!!!  If it doesn't fix it, change it back  Patches/ AntiVirus / Spyware  Upgrade/Re-install NIC driver  Replace NIC  Force speed/duplex (gig switch, Cat5 wiring?)

 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.