Confused about network configuration

Topic

New Reply

Trying to help a friend with a local network issue. He has Internet connectivity through RoadRunner (Time Warner Cable). The cable modem is connected to a router, D-Link I think. And to that router are connected a printer and 2 PCs. Also from that router is a cable to a second router (MaxTech, I think) in a second building about 100 feet away. To the second router are connected a PC and a Wireless Access Point. My confusion is with the second router. The PC and the WAP work perfectly fine and have for over a year with no issues. Today I tried to connect a second PC and from what I see Windows XP tells me that I have a network connection to the router (router #2); port LED is illuminated. But I can’t see any further or get the second PC to access the Internet. I’m by far not a network guru but can usually muddle my way through but this one has me stumped. Any suggestions? Thanks.

John
Cincinnati

Reply | Quote

Replies

Open a command prompt and execute an ipconfig /all command. Do this on the problematic PC and the one that works on router #2. Compare the output: there should be very little difference save for the IP address.

If you can post back both results we could take a stab at what is happening.

Reply | Quote

Thanks, I’ll get to that first thing on Thursday.

Reply | Quote

The 2 .bmp files are from the PC that works on router #2. The .txt file is from the laptop that does not connect. Obviously lots of differences. Any help would be appreciated.

Thanks,

John

Reply | Quote

Yes they are rather different.

In the bitmap images, we see that you have been assigned a local IP address 192.168.1.102 and subnet 255.255.255.0, which is what is expected. We also see that your router gateway is 192.168.1.1 and you are using your ISP DNS servers 4.2.2.1 and 4.2.2.2. All good and clean. Not sure about the other bitmap image that describes a second interface with a 10.60.1.5 IP address and subnet 255.255.255.192. This implies you have two network cards and perhaps a guest network configuration? anyway I think that is a red herring for these purposes. On Local Area Connection 2 you have a DHCP assigned address and correctly configured DNS.

On the laptop, you have neither DHCP assigned address, nor DNS. You also do not have an Automatic Private IP Address (APIPA). That is the default fallback in the case of a DHCP configured PC that fails to establish a IP address through DHCP. The ipconfig /all on the laptop also suggests that all is not well with the configuration or installation of the hardware.

Given the laptop reports an IP address and subnet of of 0.0.0.0 there maybe a mis-configuration of the network adapter, or an additional firewall. Do you have any extra software firewall in place – for example Mcafee or Norton Internet security, Comodo or similar? If can you disable it and see if it makes a difference.

Also verify the ethernet cable is good. Swap it with one of the good machines on the same router. Does it make a difference?

Next check the adapter properties. Go to Control Panel>Network and Internet Connections>Network Connections. You should see a network connection as below. Notice this one says connected. Yours may be different.

31140-network-connection

Right click on the network connection and select Properties. Select Internet Protocol TCP/IP and click Properties. You should see the adapter properties as shown below.31141-adapter-properties
Check that Obtain an IP address automatically and Obtain DNS server address automatically are selected.

Now select the Alternate Configuration tab and verify that Automatic Private address is selected.

If all the above is correct and required no changes, there is reasonable chance the adapter has a hardware issue. If no changes have been made, click Cancel. If you made changes to mirror the above description click OK and see if it makes a difference.

If no change, go back to the Local Area connection properties window and click configure next to the name of the ethernet adapter. The ethernet adpater properties window will appear. Select Troubleshoot and see if that resolves any issues. Make sure Use this device is selected at the bottom of the window.

31142-ethernet-properties

If it still fails, click on the Driver tab and try update or roll back the driver to see if that makes a difference.

All the above checks should walk you through establishing either a good DHCP assigned IP address or an APIPA address if DHCP is not working.

Let us how you get on.

Reply | Quote

Thanks gentlemen for your assistance. I can answer a couple of your questions even befoe I return to my friends site to go through the steps you’ve given me. First I should say that the laptop is mine and works both with a WiFi and an Ethernet cable connection. The cable I’m using at the site is a good cable. There is no extra firewall software in place at ths eite or on the laptop. I’ll be back later with what I find using your instructions.

Thanks again.

Reply | Quote

Well, I had quite a surprise a while ago. I went to my friend’s site to go through the suggestions you outlined. I changed nothing. I did try to update the laptop Ethernet driver and when asked by Windows if it shoud go to the Windows Update site, I clicked on yes figuring it would come back and tell me that it couldn’t make a connection. The message I got back was that there was not a better driver so I figured I was connected, fired up Firefox and started browsing just as if nothing had happened. I guess I’d rather be lucky than good however. The only thing that might have changed since yesterday is if the building had a power outage and the cable modem and both routers re-booted, I suppose it could have made a difference. Any thoughts? Regardless I appreciate your prompt and professional assistance.

Reply | Quote

Glad it’s working, though I’m always a little cautious about not finding a cause.

Power cycling the routers may have overcome the issue, but the other machines were allocated IP addresses. Maybe they were still within their DHCP lease time and a stuck DHCP server in one of the routers may have caused the issue on the laptop while retaining the capability to route internet access.

Ummm, now there’s a thought: could it be that both routers are (were?) configured to run DHCP? There can be only one DHCP server on a network. If more than one DHCP server exists you may encounter similar issues.

One to keep an eye on perhaps?

Reply | Quote

I’ll have to double check the settings for DHCP. Good thought and thanks again.

John

Reply | Quote

For a small network like this I would replace the second router with a switch and end the headaches unless there is some special need to use a second router.The best scenario for router two is to turn off routing, NAT and DHCP so it acts like a switch.

Reply | Quote