Losing Internet connection when connecting cable

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Izak95

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Hi,

I`ve got two ethernet card:
- Ethernet 1: computer network on static ip address
IP address: 1.1.1.9 and subnet mask: 255.255.255.0

- Ethernet 2: Providing internet
IP address: DHCP

When connecting the cable to the ethernet card 1, I am losing the internet connection.

Is there any reason why this is happening. I`ve got some wireshark files if needed.

Many thanks,
 

Fireflycph

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What is the Subnet mask and DNS settings?

Also make sure that the IP address is in the same as the DHCP settings in the router. An address that's outside the scope but on the same network.

Which ip do you get when connected by DHCP?

Run an "IPCONFIG /ALL" from a command prompt and post the result here.
 

Izak95

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Dec 2, 2021
Messages
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Hi,
Ill check this tomorrow. Here is a link to the wireshark files in case we can find this info...


Attached is the subnet mask of the ethernet card:
 

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Fireflycph

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That's your problem.

Change the static IP to "192.168.1.251", and set all the other settings as they are in the DHCP. It should work.
 

Izak95

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Dec 2, 2021
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What is the Subnet mask and DNS settings?

Also make sure that the IP address is in the same as the DHCP settings in the router. An address that's outside the scope but on the same network.

Which ip do you get when connected by DHCP?

Run an "IPCONFIG /ALL" from a command prompt and post the result here.
Here is the subnet mask of the Ethernet card 2 providing internet
That's your problem.

Change the static IP to "192.168.1.251", and set all the other settings as they are in the DHCP. It should work.
Ok, so the ethernet card settings will be as below:

Ethernet card 1:
IP address 1: 1.1.1.9
Subnet mask: 255.255.255.0
Default Gateway:

Ethernet card 2:
IP address 1: 192.168.1.251
Subnet mask: 255.255.255.0
Default Gateway:192.168.1.1

Is that correct? Why changing it would resolve it? Thanks
 
Last edited:

Fireflycph

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No. Ethernet card 1 can't connect since it's on a different network. That's the IP you need to change.

What is the reason you have such a static ip (1.1.1.9)?
 

Izak95

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I have no idea why they set up the IP network with 1.1.1.x . There are several devices on this IP range, it might be difficult to change them all.

Is it not possible to create a bridge to share the internet connection between both network? What are my options if I can only change the settings of the ethernet card 2 and not card 1.

I cannot change the settings of ethernet card 1 as I would have to change all the IP addresses of the existing devices on this network.

Thank you
 

Fireflycph

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It must have been done this way for a reason. Most likely to isolate some devices from the outside (Internet).
Who set this up? What are the devices that Ethernet 1 connects to?
I don't think it's possible to setup a routing feature for just one IP on a standard router.
Can you add a cable so both are connected at all times?
 

zx10guy

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Why are you doing this setup? Is this box acting as a router for other devices? If so, why are you not using a dedicated firewall/router to do this?

The other thing is using the 1.1.1.x address space is asking for trouble. There are resources on the Internet that resolve to that address space and if you happen to connect to domain on the Internet that has an IP in that address space, you'll never reach it. You should use the reserved private IP address space specified in the IP addressing RFC which are: 10.x.x.x, 172.16-31.x.x, and 192.168.0-255.x.
 

TerryNet

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IF there is a gateway specified for ethernet 1 that is why you lose internet access when connecting the ethernet 1 cable. For that static IP configuration the gateway should be blank.

As zx10guy said you could run into trouble using 1.1.1.x addresses instead of private IP addresses, but using that is not causing your loss of internet access.
 

Izak95

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It must have been done this way for a reason. Most likely to isolate some devices from the outside (Internet).
Who set this up? What are the devices that Ethernet 1 connects to?
I don't think it's possible to setup a routing feature for just one IP on a standard router.
Can you add a cable so both are connected at all times?
I agree.

The devices connected to Internet are Air Conditionining units. Another engineers set them up and I`ve just been asked to provide a remote connection to the site via Teamviewer. We`ve added another Ethernet card to connect it to internet but when connecting both network, we lose the internet.

What do you mean by adding a cable. We`ve got two cables already, one connected to each ethernet card.
 

Izak95

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Dec 2, 2021
Messages
8
Why are you doing this setup? Is this box acting as a router for other devices? If so, why are you not using a dedicated firewall/router to do this?

The other thing is using the 1.1.1.x address space is asking for trouble. There are resources on the Internet that resolve to that address space and if you happen to connect to domain on the Internet that has an IP in that address space, you'll never reach it. You should use the reserved private IP address space specified in the IP addressing RFC which are: 10.x.x.x, 172.16-31.x.x, and 192.168.0-255.x.
I am just trying to provide internet and teamviewer access to the PC. I agree about the private IP address. Could that create an IP conflict or is it only if I am trying to connect to this address space?
 

Izak95

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Joined
Dec 2, 2021
Messages
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IF there is a gateway specified for ethernet 1 that is why you lose internet access when connecting the ethernet 1 cable. For that static IP configuration the gateway should be blank.

As zx10guy said you could run into trouble using 1.1.1.x addresses instead of private IP addresses, but using that is not causing your loss of internet access.
That`s right, for the ethernet 1, the gateway is blank. Ok, I agree about using 1.1.1.x is wrong but it was set up by another engineer. I`ll have to change a lot of IP address if I need to change the IP range.

Should I create a bridge between both connections? Could that be the problem? or do I need to set up a route in Windows?
 

Izak95

Thread Starter
Joined
Dec 2, 2021
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I`ve got the wireshark files for both connections if anyone got a software to debug it....
 

TerryNet

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I'm not seeing any reason why the internet access is lost. Maybe Windows is refusing to use the USB connection when the integrated ethernet is connected? But that doesn't make sense to me.

Please show for when both ethernet cables are connected ...

Open a (black) Command Prompt window:
Hold the Windows logo key and press r; in the Run box type cmd and click on OK.
(In Windows 10 you may have to use some other procedure to get a Command Prompt window.)

Type the following commands:

IPCONFIG /ALL

[Note that there is no space between the slash and ALL.]

Ping 192.168.1.1

Ping 8.8.4.4

Ping Yahoo.com


[Press ENTER after each command.]

Right click in the command window and choose Select All, then hit Enter.
Paste the results in a message here.

If necessary use a text file and removable media to copy the results to a computer with internet access.
 
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