Question : Intermitent Internet on Multiple PCs on LAN but not all of them, seems to be DNS issue

I have a small network workgroup of 10 or so Windows XP PCs. About two weeks ago 4 of them started experiencing issues with intermittent problems browsing the web. When the problem occurs the internet become unbrowsable but works if you use a website's IP address instead so it seems DNS related. The issue occurs several times throughout the day on the affected machines and resolves itself usually within 5 to 10 minutes of the problem starting without any user intervention. It will then start happen again at some point during the day perhaps an hour later or perhaps 10 minutes later. The local LAN works fine when this problem occurs as I can browse to and ping other machines and devices on the LAN fine during the time that the internet doesn't work BUT I CAN'T ping the router's IP when it happens. The router acts as the DHCP server, it is a Netgear Prosafe FVX538 with version 2.1.3-17 firmware. The kicker is that the other 6 computers on the network work just fine all of the time and have no issues. The issue randomly occurs on the affected machines and it doesn't happen to all of them at the same time. It will start happening on the one I'm working on so I'll go to another and it will be fine but then that one will start acting up 10 minutes later so I go back to the original machine and it has fixed itself and it working again. Rebooting the machine seems to fix the problem temporarily. All of the computers are on identical hardware both the ones that have the issue and the ones that don't. There is no internet security or firewall software installed, just the Windows firewall.

Code Snippet:

         
           
             1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:

           
           
             ipconfig /all
 
Windows IP Configuration
 
        Host Name . . . . . . . . . . . . : day-pc
        Primary Dns Suffix  . . . . . . . :
        Node Type . . . . . . . . . . . . : Hybrid
        IP Routing Enabled. . . . . . . . : No
        WINS Proxy Enabled. . . . . . . . : No
 
Ethernet adapter Local Area Connection:
 
        Connection-specific DNS Suffix  . :
        Description . . . . . . . . . . . : Realtek RTL8168/8111 PCI-E Gigabit E
thernet NIC
        Physical Address. . . . . . . . . : 00-19-DB-5F-91-11
        Dhcp Enabled. . . . . . . . . . . : Yes
        Autoconfiguration Enabled . . . . : Yes
        IP Address. . . . . . . . . . . . : 192.168.50.148
        Subnet Mask . . . . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . . . . : 192.168.50.1
        DHCP Server . . . . . . . . . . . : 192.168.50.1
        DNS Servers . . . . . . . . . . . : 192.168.50.1
        Primary WINS Server . . . . . . . : 192.168.50.1
        Lease Obtained. . . . . . . . . . : Thursday, January 10, 2008 5:04:41 P
M
        Lease Expires . . . . . . . . . . : Friday, January 11, 2008 5:04:41 PM

           
         

Open in New Window

Select All

Answer : Intermitent Internet on Multiple PCs on LAN but not all of them, seems to be DNS issue

There should be no poblem in pointing the client to the router's internal IP for DNS. In most scenarios this is the perferred method.

I agree with you techworksolutions, that you problem is the inability of the client computer to contact the router during this period. You say the router will still route external traffic though. The first thing I would try is to switch the cables and the ports around to see if the problem follows them or stay on the computers.

If it stays on the computers, I would look to uninstall TCP/IP and reinstall. Don't just reinstall without uninstalling. You'll also want to research repairing the winsock and LSP layer fo good measure. Then I would move on to swapping NICs, and finally look for any malware that may have gotten onto the machines.

You will also want to update the firmware to the latest version (if its not already). Does the device have any reporting that you can look at? perhaps one computer is chattering and causing collisions, or the device has some sort of throttle setting.

The device seems to have 8 100MB ports and 1 GB port. So you have only 9 computer, correct? there are no other hubs or switches?