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    Archived pages: 1 . Archive date: 2014-09.

  • Title: FHTC Network Troubleshooting Flowchart
    Descriptive info: .. START.. Windows Workstation Unable to Access a Network Service.. Gather Clues.. A.. Ask Questions.. i.. What were you doing when the problem occurred?.. ii.. Have there been any recent changes to the network?.. B.. Have the customer recreate the problem while you watch.. While watching, check for obvious user errors (ID10T errors), such as Caps-Lock being on.. Do other workstations on the LAN have the same problem?.. Yes.. or.. No.. Are the switch, hub, or wireless access point's power & link-lights lit?.. ping.. *.. the destination by name.. Successful?.. Possible Solutions.. Specific service is down on destination server.. The server itself is up and communicating, but the specific service you are trying to access is down for some reason.. Figure out why the service is down (look at configuration, recent updates, & logs), and bring it back up.. If it is still up but not responding, restart it.. Misconfigured firewall.. Network firewall may be blocking all access from your LAN to specific service port on destination server.. Configure it to allow your LAN access to service.. C.. Malware infection on destination server or it has been hacked.. Scan server for malware infection using anti-virus software such as MalwareBytes.. Check for signs of break-in (look at the logs).. If All Else Fails.. Sniff the network with Wireshark on the server while recreating the problem.. See if packets are actually being sent to the correct port and if there are any replies.. Look for packets containing diagnostic or error messages.. Search the Internet.. See if others have had the same problem, and if so, how they solved it.. Problem Solved?.. Document Your Solution.. FINISHED.. the destination by IP address.. Name of destination unable to be resolved for one of the following reasons:.. Name not configured in DNS server.. Make sure proper records (A, CNAME, MX, etc) for name are found in DNS zone file on your nameserver.. DNS resolver or nameserver down or locked-up.. Verify that your DNS servers are running properly.. If not, figure out why and bring them back up.. iii.. WINS server down or locked-up.. Verify that your WINS servers are running properly.. iv.. DHCP server is giving out wrong DNS or WINS server addresses.. Properly configure DHCP server’s scope to provide correct DNS & WINS server addresses.. Sniff the network with Wireshark while recreating the problem.. Pay special attention to any name resolution packets (DNS, NetBIOS, LLMNR).. Execute:.. ipconfig /all.. on at least two LAN workstations having the same problem.. What type of IP addresses?.. DHCP starting with 169.. 254 (APIPA).. DHCP IP addresses.. Static IP addresses.. DHCP server down, not configured properly, or not installed on LAN.. Start it back up, configure it properly, or install it.. Locked-up switch, hub, or access point.. Unplug it and plug it back in.. If it is managed and still unresponsive, try resetting it back to factory default settings.. Misconfigured managed switch or access point.. Configure it properly.. If all else fails, reset it to factory default settings.. D.. Bad switch, hub, or access point.. Power lights are still lit, but link lights probably are not.. Swap it with another one to test.. Replace if bad.. E.. Chatty NIC on LAN.. Malfunctioning or faulty NICs sometimes become "chatty", putting out excessive packets on the network and using up all of its bandwidth, which affects all workstations in that broadcast domain.. Unplug the power from the computer with the chatty NIC and then plug it back in.. If this doesn't fix the problem, the NIC is probably bad, in which case it will have to be replaced or disabled.. Default Gateway router.. On which LAN is the destination located?.. Same LAN as workstation.. Different LAN on the Internet.. Different LAN, but still on this organization's network.. Destination down or locked-up.. Boot or reboot it.. Plug it in first if it is unplugged from power.. Bad cable or cable unplugged between destination and switch/hub.. If the link-lights are not lit on the destination, this is probably the problem.. Misconfigured IP settings on destination.. Check its IP settings and correct them if necessary.. DHCP server is giving out wrong subnet mask.. Properly configure DHCP server’s scope to provide correct subnet mask..  ...   the destination LAN.. Not past the local router.. All the way to the destination LAN, but no response from destination.. Are the router’s power & link-lights lit?.. Misconfigured router.. The router may be configured with the wrong IP addresses for its interfaces.. Configure them properly.. Rogue DHCP server giving out wrong IP addresses.. If addresses are from DHCP, verify that they are from the correct IP network for this subnet.. If not, there could be a rogue DHCP server dishing out incorrect addresses.. Find it and shut it down.. DHCP server is giving out wrong default gateway address.. Properly configure DHCP server’s scope to provide correct default gateway router IP address.. Router is on a different switch/hub, and that switch/hub is down or locked-up.. Power-on or reset switch/hub.. Power unplugged from router.. Plug it in.. Bad cable or cable unplugged between router and switch, hub, or access point.. If the link-lights are not lit on the router, this is probably the problem.. Locked-up router.. If it is still unresponsive, you may have to reset it back to factory default settings.. Bad router.. other computers on the same LAN.. Power unplugged from switch, hub, or access point.. Restart the affected workstation.. Problem solved?.. Problem Solved.. Is the Link-Light on the NIC lit?.. What type of IP address?.. No IP address.. Valid Static or DHCP.. NIC driver not installed or wrong NIC driver installed.. Install or update NIC driver in Device Manager.. Faulty NIC.. Try a different NIC in the workstation.. Faulty application software.. Check app’s settings.. Try reinstalling app.. Check app manufacturer’s website.. If it is a web browser, clear the cache & check the proxy settings.. Disable Windows firewall.. Check with admin of network firewall to see if workstation is being blocked.. Invalid entry for destination name in.. \windows\system32\drivers\etc\hosts.. file.. It normally should not be listed in this file at all.. Insufficient rights to access service.. Check with admin of service or the server itself to see if user has sufficient rights or their account has been disabled.. User is using incorrect username and/or password.. Malware infection.. Scan system for malware infection using anti-virus software such as MalwareBytes.. See if packets are actually being sent to the correct addresses and if there are any replies.. Incorrect DNS server or WINS server address.. Compare these addresses with the settings on another workstation that is working on the LAN.. the default gateway’s IP address.. Incorrect IP address or subnet mask.. Compare with the settings on another workstation that is working on the LAN.. Incorrect, outdated, or misconfigured NIC driver.. Verify NIC driver in Device Manager, and don’t forget to check the NIC’s settings, such as connection speed.. Reset Windows TCP/IP stack using.. netsh int ip reset.. command.. Reboot after executing command and reconfigure the NIC’s IP settings.. Faulty cable.. Test with cable tester or swap cables.. Sometimes link-lights lie.. Make sure cable is not too long.. If Wireless, lost connection to access point.. Make sure workstation is close enough to access point.. Check for interference.. Make sure wireless NIC is configured with correct SSID & passphrase.. H.. Bad entry in local routing table.. View it using the.. route print.. command, and compare it with the routing table on another workstation that is working on the LAN.. When All Else Fails.. Incorrect subnet mask or default gateway.. Cable unplugged from NIC or switch/hub.. Faulty or disabled NIC.. Check if it is enabled in Windows and BIOS setup.. Test with loopback.. Swap with another NIC.. Bad port or uplink port on switch/hub.. Move the cable to a different port.. Disabled port on managed switch.. Login to switch and enable port.. *NOTE:.. If you are unable to ping a web site using the normal.. command (which uses ICMP that may be blocked for security reasons), try pinging it with TCP using the.. psping.. command available from the PsTools software toolkit at.. http://download.. sysinternals.. com/files/PSTools.. zip.. Examples:.. psping www.. fhtc.. edu:80.. psping 157.. 166.. 239.. 177:80.. Click.. here.. for a graphical version of this flowchart.. for a simpler version of this flowchart that is compatible with older browsers.. All content copyright.. Flint Hills Technical College.. 2014.. Written and designed by Adam Starr.. All rights reserved..

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