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help!! No network & No Internet connectivity

Posted on 2016-11-28
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Last Modified: 2017-01-02
Came into work this morning to a basically a crippled network.

No internet connectivity (although ISP have checked it an said its online)

Pinging internal hosts via their name fails, pinging an ip address works, but with a few fails (out of 20 pins 3 fail)

Just trying to figure out how to use wireshark to sniff the network for a possible ip conflict

Any ideas

Thanks
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Question by:mudcow007
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4 Comments
 
LVL 17

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by:
John Tsioumpris earned 250 total points
ID: 41903983
Things to check:
  • Your switches....try to use another one
  • Client NICs
  • small switches 5-8 port that are used when you are short on network outlets
  • check if there is software issue -Virus
When something of the above fails they generate massive packet loads that cripple the networks...
The first action would be to connect a machine directly to the Intenet and then add machines one by one
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LVL 4

Assisted Solution

by:Marcos Santo
Marcos Santo earned 125 total points
ID: 41903986
check your local DNS settings, that is probably the problem.
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LVL 28

Assisted Solution

by:Dr. Klahn
Dr. Klahn earned 125 total points
ID: 41903988
Before sniffing the network, try some simple hardware troubleshooting.

Disconnect everything from the cable/DSL modem. Power off the modem, wait two minutes, power back on.  See if the status lights indicate that it's online.

If the modem comes online, plug a PC directly into the modem's LAN port.  Turn it on and see if it can get an IP assignment from the modem via DHCP when the PC comes up.  If so, the problem's not in the modem.

Now back up one level and connect the modem to its associated switch / router / hub or however you're distributing internet access from the modem to the LAN.  Disconnect everything from the switch / router / hub.  Power off the S/R/H, wait two minutes, power back on.  See if the status lights indicate normal operation.

If the switch / router / hub comes online, plug a PC directly into one of the S/R/H's LAN ports.  Turn it on and see if it can get a DHCP IP assignment when it comes up.   If so, the problem's not in the S/R/H.  If not, the problem's in the primary S/R/H.

If you get this far then the problem's out on the LAN.  If there are subsidiary S/R/Hs turn all off.  For each subsidiary S/R/H, power on and check to see if the problem persists at the PC (still) connected to the primary S/R/H.  If so, the problem's in that S/R/H or in a PC on the subnetwork it serves.  If not, turn that subsidary S/R/H off and go check the next one.  Repeat until all are tested.

if the problem still persists, at this point all the easy troubleshooting is done and you can start sniffing.
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Author Comment

by:mudcow007
ID: 41904040
Hello all

cheers for the suggestions. It looks to be a failed switch port. Im yet to figure out which one.

Disconnected the switch an network has now become active

Thanks for the suggestions

Danny
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