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No Internet KB1039344

KB1039344

Description:  No Internet

Common customer description:

-I do not have internet right now and everyone else is fine.

-I don’t have internet and everyone else is also affected by this.

Probing questions:

When did this start happening?

How many people are affected?

Are you able to access local resources?

What is their current IP address?  (Do they have an APIPA address? Or a normal Private IP address?)

Can they ping outside of the network by IP?

Steps to isolate:  To isolate the problem, work from the inside out.  So in this case, rule out the PC then work your way into the network.  Follow these steps:

 

  1. Start off by Pinging the loopback address of the computer. For all computers, the IPv4 loopback is 127.0.0.1 and IPv6 is ::1  (If successful proceed to the next step)
  2. Ping the computers current IP address, you can get this by typing IPCONFIG in a command prompt window. (If you get an APIPA address which is 169.254.x.y, the computer is unable to reach DHCP for an IP address:  If this is the case, go to the DHCP section below)
  3. If the first two steps work fine, then it’s time to ping the Default Gateway. Like before, you get the default gateway but typing IPCONFIG in a command prompt window.
  4. If this fails, it is most likely something to do with either Cabling or the switch, But if it succeeds you may need to do is reboot the modem and test connectivity by trying to ping outside the network (THIS SHOULD ONLY BE DONE IF MULTIPLE USERS ARE AFFECTED BY THIS SAME ISSUE). To test this, you can do this by pinging google.com or getting it’s IP address by pinging it on YOUR MACHINE and having the user trying to ping the IP address.  If you are able to ping by IP and not by name go to the DNS

After following these steps you’ll be able to determine where it is that the communication to the outside world is failing.  Once we find the resolution we will be able to find out what is wrong at this point.

 

Steps to resolve: Since there are multiple points of failure one a network, you need to have a basic understanding on how a network is laid out to be able to accurately diagnose the issue.  Typical setup is PC à Switch à Router//Firewall à Modem à Outside World.

FIRST STEPS:  Typically, one of the first things you can do is restart//reboot the Modem and Firewall.  If this doesn’t work, proceed with the other processes (ONLY DO THIS IF MULTIPLE USERS ARE AFFECTED, IF THERE IS ONLY ONE SKIP THIS AND PROCEED TO THE NEXT STEPS).

 

DHCP:  If you get an APIPA Address on the computer//computers that cannot reach the internet, that narrows down your troubleshooting drastically.  Since the computer cannot reach DHCP(The Server usually some cases, this will be the router//firewall).  To further troubleshoot this follow these actions:

 

  • Have the user take a look at the cabling of the machine and determine the following:
    • Unplug and plug the Ethernet cable in
    • Ask the user to follow the cable to where it’s connected to, is it labeled?
      • If it’s connected to a switch, is the switch on? Is it connected to another switch or the firewall//router?
      • If it’s connected to a wall jack//keystone, is it labeled? If so ask if the user can track it to the network rule and see if changing the ports on the switch works
    • Is the Server powered on? If not power it on.
      • If it is powered on, log into it and load up DHCP under administrative tools
      • Once in DHCP, take a look at the lease pool size and then take a look at the leased addresses in the range are all taken up or not. Expand the Lease pool if needed.
      • Reboot the Server if needed.

DNS:  For situations where you can ping by IP address but not by name.  You should have determined this by trying to ping google.com by name and then by IP by the isolation steps above, follow these actions to further troubleshoot:

 

  • We will need to know the DNS setting currently, Type IPCONFIG /ALL in a command prompt window to get this information. Chances are is that the DNS configured is misconfigured to what it’s supposed to be.  DNS is supposed to be configured with the Domain Controller (PDC).
    • If it’s not configured at all, you will need to determine if it’s being statically assigned or dynamically assigned. To do this you will need to go into the properties of the NIC (Network Interface Card) and see if it’s setup.  If it’s dynamic, you can try manually setting the DNS on the NIC.  This should resolve the problem.
    • At this point if it still doesn’t work, try to perform an IPCONFIG /FLUSHDNS and IPCONFIG /REGISTERDNS commands from command line.

 

Additional considerations: In the worst case, if nothing else works.  We will need to on-site the issue.  Consult Tier 2 and ask for further advice.