Second network adaptor causing the first to lose connectivity

[Anifinity]

Hi guys,

I recently installed a second network adapter in my computer. This second adapter is attached to its own cable modem and has its own dynamic IP address and is named Ethernet 3. In addition to Ethernet 3, I also have my main motherboard network adaptor named Ethernet which is connected to its own unique cable modem from a completely different ISP.

Ethernet is a gigabit adapter connected to a 100/5 cable connection
Ethernet 3 is a gigabit adapter connected to a 7.5/0.5 cable connection

The issue is, When I have traffic passing through both adapters the connections work fine for several minutes and then the Ethernet 3 connection causes Ethernet, my main connection, to stop working; I am no longer able to ping out or resolve web pages. The moment I disable Ethernet 3 my Ethernet (main) adapter immediately starts working again.

I want to be able to run both adapters simultaneously. Ethernet 3 is only going to be used with a specific program on the computer while Ethernet will be used for everything else. I have already manually changed the Interface metric of Ethernet to '20' and Ethernet 3 to '30' setting up my 100mbps line as the primary however this does not seem to be working.

Does anyone know how I can make it so my main adapter (Ethernet) is set as the default used for everything while Ethernet 3 is only used when I manually setup its dynamic IP in my chosen program?

I am running Windows 8.

Thanks.

 

[EvilAlchemist]

I have never tried what you are attempting.

A workaround that comes to mind is virturalize and have the program run on the vm with that interface as its only connection.

Not sure what kind of app you have and if it requires interaction or not.

 

[Anifinity]

I have never tried what you are attempting.

A workaround that comes to mind is virturalize and have the program run on the vm with that interface as its only connection.

Not sure what kind of app you have and if it requires interaction or not.

this would work for the program I have setup, however I dont want to be forced into virtualization. Worst case scenario I can dedicate another computer to that connection but I would rather be able to use the two connections on the same computer if at all possible

 

[Eickst]

Are both of your adapters set for dhcp? Do they both show routes to 0.0.0.0?

 

[Anifinity]

Are both of your adapters set for dhcp? Do they both show routes to 0.0.0.0?

Yes, both adapters are set for DHCP. I do not have a static IP on either adapter. Ethernet is connected to a router while Ethernet 3 is direct to secondary modem.

 

[Shadowspawn]

I too have two connections to my laptop right now. One is connected to my satellite modem, the other is a wireless connection to a wireless router that has a storage device on it. The wireless is just a shared server for everybody I work with.

The difference between my setup and yours is that only one subnet is available off of my wireless, and it is a private range. There is no internet connection via that route. So my routing table has that subnet out that interface and that is it.

Is your program only being used to communicate to a specific subnet, or group of subnets? Or is it accessing the internet in general. If it is specific, then you can add routes to your routing table listing those subnets as out that specific interface.

I suspect your problem isn't a routing issue though. I think you have some sort of conflict between the two NICs that is causing one of them to shut down. If it was a routing issue, the NIC wouldn't be losing connectivity.

 

[Anifinity]

I too have two connections to my laptop right now. One is connected to my satellite modem, the other is a wireless connection to a wireless router that has a storage device on it. The wireless is just a shared server for everybody I work with.

The difference between my setup and yours is that only one subnet is available off of my wireless, and it is a private range. There is no internet connection via that route. So my routing table has that subnet out that interface and that is it.

Is your program only being used to communicate to a specific subnet, or group of subnets? Or is it accessing the internet in general. If it is specific, then you can add routes to your routing table listing those subnets as out that specific interface.

I suspect your problem isn't a routing issue though. I think you have some sort of conflict between the two NICs that is causing one of them to shut down. If it was a routing issue, the NIC wouldn't be losing connectivity.

The application accesses the internet in general. How can I find out if it is indeed a conflict issue?

Ethernet is a Realtek gigabit adapter (Realtek 8110SC)
Ethernet 3 is an Intel Pro/1000 CT gigabit adapter


Edit 1: After looking into things the pci-e port I was using was on the same IRQ as my LAN interface. I have since moved the intel adapter to another pci-e port with its own IRQ assignment. The issue still occurs.
Edit 2: After investigating a bit more it looks like it may be a DNS/DHCP issue after all as I was able to pung google and msn by IP but not by domain. Thinking this, I have set one of my adapters up using google DNS and disabled DHCP however the issue seems to still occur.

C:Windowssystem32>netsh interface ip show address

Configuration for interface "Ethernet"
DHCP enabled: Yes
IP Address: 192.168.1.136
Subnet Prefix: 192.168.1.0/24 (mask 255.255.255.0)
Default Gateway: 192.168.1.1
Gateway Metric: 20
InterfaceMetric: 20

Configuration for interface "Ethernet 3"
DHCP enabled: No
Default Gateway: 69.172.151.1
Gateway Metric: 30
InterfaceMetric: 30

Configuration for interface "Loopback Pseudo-Interface 1"
DHCP enabled: No
IP Address: 127.0.0.1
Subnet Prefix: 127.0.0.0/8 (mask 255.0.0.0)
InterfaceMetric: 50

 

[Anifinity]

Scratch that last post, it looks like when the connection goes down and I ping using the main adapter it is unable to resolve using IP or domain.

To summarize so far:

Ethernet = primary connection with unique modem (realtek NIC)
Ethernet 3 = secondary connection with unique modem (intel NIC)

Ethernet = interface metric value of 20
Ethernet 3 = interface metric value of 30

Under Windows' "Adapters and Bindings" section I have ordered Ethernet above Ethernet 3.


C:\Windows\system32>netstat -rn
===========================================================================
Interface List
18...bc ae c5 17 e2 b6 ......Realtek PCI GBE Family Controller
17...68 05 ca 16 92 01 ......Intel(R) Gigabit CT Desktop Adapter
1...........................Software Loopback Interface 1
12...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter
13...00 00 00 00 00 00 00 e0 Teredo Tunneling Pseudo-Interface
15...00 00 00 00 00 00 00 e0 Microsoft 6to4 Adapter
16...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #3
===========================================================================

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 69.172.151.1 69.172.151.17 60
0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.136 40

in addition I have disabled DHCP for Ethernet 3 and set it up for my dynamic IP address.

C:Windowssystem32>netsh interface ip show address

Configuration for interface "Ethernet"
DHCP enabled: Yes
IP Address: 192.168.1.136
Subnet Prefix: 192.168.1.0/24 (mask 255.255.255.0)
Default Gateway: 192.168.1.1
Gateway Metric: 20
InterfaceMetric: 20

Configuration for interface "Ethernet 3"
DHCP enabled: No
Default Gateway: 69.172.151.1
Gateway Metric: 30
InterfaceMetric: 30

Configuration for interface "Loopback Pseudo-Interface 1"
DHCP enabled: No
IP Address: 127.0.0.1
Subnet Prefix: 127.0.0.0/8 (mask 255.0.0.0)
InterfaceMetric: 50

When Ethernet stops functioning, Ethernet 3 continues on its way without interruption. If I disable Ethernet 3 and re enable it Ethernet starts working on its own. If I instead disable Ethernet and re enable it I can also restore connectivity.

I have made sure my Intel NIC is assigned an IRQ different than my motherboard's realtek LAN interface.


This issue is really frustrating me, I have no idea what else to try.

 

[jimh425]

What is the IP address for Ethernet 3? I would put them on separate subnets. I can't tell if you've done that it not, but maybe I missed it in your posts.

 

[Eickst]

Try deleting the unused 0.0.0.0 route to the 69.172.151.1 address.

 

[tporter]

This is DEFITELY a routing issue. Windows cannot handle 2 default routes correctly. This has been an issue for years. Windows seems to randomly choose one card or the other to out on initial connections. If you need 2 nics you MUST use static on one of them so you can leave off the default gateway. Manually put in any routes you want to go out the nongatewayed nic. Also you could use a crap pc with Linux and 3 nics to use as dual wan software router which would solve the issue if your trying to use load balacing or failover...

 

[EvilAlchemist]

Just an idea, do u have an extra Intel nic, so u can disable Realtec and just use Intel nic drivers ??
Would eliminate a driver conflict ???

 

[Anifinity]

What is the IP address for Ethernet 3? I would put them on separate subnets. I can't tell if you've done that it not, but maybe I missed it in your posts.

They are already on different subnets. Ethernet is on subnet 255.255.255.0 through mt router while Ethernet 3 is using 255.255.255.192 direct to my secondary modem.

Try deleting the unused 0.0.0.0 route to the 69.172.151.1 address.

Instead of deleting the persistent route I changed the adapter back to DHCP. The route was automatically added when I configured the dynamic IP's gateway on the interface. This has since been removed and I have put the interface back on DHCP.

This is DEFITELY a routing issue. Windows cannot handle 2 default routes correctly. This has been an issue for years. Windows seems to randomly choose one card or the other to out on initial connections. If you need 2 nics you MUST use static on one of them so you can leave off the default gateway. Manually put in any routes you want to go out the nongatewayed nic. Also you could use a crap pc with Linux and 3 nics to use as dual wan software router which would solve the issue if your trying to use load balacing or failover...

unfortunately I do not have access to a static IP. I was not trying to use the NIC's for load balancing or failover, I just wanted 2 NIC's with 2 IP's for 2 connections. 1 connection would be used for everything but one of my apps while that app would use the dynamic IP of the second modem exclusively.

What kind of routing changes would I need to make? would it only work with a static IP?

Just an idea, do u have an extra Intel nic, so u can disable Realtec and just use Intel nic drivers ??
Would eliminate a driver conflict ???

unfortunately I do not have another intel NIC. Even if I did have another, I am out of pci-e slots so I would not have anywhere to put it.


any other ideas that I might be able to try?

Here is my current IPv4 routing table

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.136 40
0.0.0.0 0.0.0.0 69.172.151.1 69.172.151.17 60
69.172.151.0 255.255.255.192 On-link 69.172.151.17 286
69.172.151.17 255.255.255.255 On-link 69.172.151.17 286
69.172.151.63 255.255.255.255 On-link 69.172.151.17 286
127.0.0.0 255.0.0.0 On-link 127.0.0.1 306
127.0.0.1 255.255.255.255 On-link 127.0.0.1 306
127.255.255.255 255.255.255.255 On-link 127.0.0.1 306
192.168.1.0 255.255.255.0 On-link 192.168.1.136 276
192.168.1.136 255.255.255.255 On-link 192.168.1.136 276
192.168.1.255 255.255.255.255 On-link 192.168.1.136 276
224.0.0.0 240.0.0.0 On-link 127.0.0.1 306
224.0.0.0 240.0.0.0 On-link 192.168.1.136 276
224.0.0.0 240.0.0.0 On-link 69.172.151.17 286
255.255.255.255 255.255.255.255 On-link 127.0.0.1 306
255.255.255.255 255.255.255.255 On-link 192.168.1.136 276
255.255.255.255 255.255.255.255 On-link 69.172.151.17 286
===========================================================================

it looks like the Ethernet 3 interface is correct, all traffic appears to be routing to the gateway 69.172.151.1, which is correct.

 

[Eickst]

Change the secondary adapter back to manual ip but do not enter a gateway address. P

 

[Anifinity]

Change the secondary adapter back to manual ip but do not enter a gateway address. P

This would just take down my internet and there would be no where for the packets to go?

 

[Metraon]

I dont know if windows 8 supports it, but have you tried ForceBindIP ? When I had problems with Hamachi back in the days, I used this program to fix connection binding, when the Adapters and Bindings didn't make a change.

 

[jimh425]

You can assign static ips to both nics. You just have to make sure they have the right gateway and dns servers. It won't change the address of the modems. I don't think that fixes your fundamental problem.

I think you will need a switch that controls what apps have access to route traffic from one app/range of addresses to only one modem. The problem is all of your traffic either in or out can go to either network. It's also possible one of your isps is entering into the picture depending on what traffic you are passing.

I think the vm is the easiest solution to keep the traffic isolated and has the advantage if you ever want to use a second physical computer and keeps you from making changes that might indirectly impact your app. You'll also know what has to be on the second computer.

 

[Eickst]

This would just take down my internet and there would be no where for the packets to go?

Don't you have two cable modems? If you have one adapter with a default gateway and one without where do you think the packets will go?

 

[Biznatch]

Yes this is 100% a routing issue. You cannot have 2 default gateways with windows.

Setup your main network with the the full IPconfiguration. IP, Gateway, DNS etc. Under "adapter settings", hit alt, then go to 'Advanced' dropdown, then advanced settings. Make sure the main adapter is the top of the list (first bound adapter).

For the second adapter, you only need the IP address/subnet. But, without a gateway, it will only route packet destined for the subnet of that network adapter. Since this is not what you want, you will need to add a static route to force traffic over the second adapter. The problem is, I don't know what service you are trying to redirect.

 

[Nate7311]

Without a separate Multi-WAN Router and a 1:1 scenario, you cannot accomplish this in Windows. And furthermore, two bare Cable connections directly to your Windows 8 box, would make me nervous.

 

[Eickst]

Without a separate Multi-WAN Router and a 1:1 scenario, you cannot accomplish this in Windows. And furthermore, two bare Cable connections directly to your Windows 8 box, would make me nervous.

You can do it with one adapter set for static with no gateway and a static route for whatever ip his application is going to.

Windows has no problem with being connected to disjointed networks it just doesn't do we'll with multiple default gateways.

 

[Anifinity]

Yes this is 100% a routing issue. You cannot have 2 default gateways with windows.

Setup your main network with the the full IPconfiguration. IP, Gateway, DNS etc. Under "adapter settings", hit alt, then go to 'Advanced' dropdown, then advanced settings. Make sure the main adapter is the top of the list (first bound adapter).

For the second adapter, you only need the IP address/subnet. But, without a gateway, it will only route packet destined for the subnet of that network adapter. Since this is not what you want, you will need to add a static route to force traffic over the second adapter. The problem is, I don't know what service you are trying to redirect.

How would this work out? the 2 NICS are on completely seperate networks and would not be able to see the same primary gateway. For example, my main connection uses gateway 192.168.1.1 on its own subnet while the second NIC is on gateway 192.168.0.1, also with its own subnet. The moment I configure the second adapter for no gateway, it loses connection and displays "unidentified network". Route print shows only the 0.0.0.0 default connection for gateway 192.168.1.1 but because the 2nd NIC is on its own network and uses its own segregated path to its own modem, it cannot see the primary NIC's gateway.

I either dont understand what you're asking me to do or there is a misconception on how this is setup.

I dont know if windows 8 supports it, but have you tried ForceBindIP ? When I had problems with Hamachi back in the days, I used this program to fix connection binding, when the Adapters and Bindings didn't make a change.

It looks like Windows 8 does not support forcebindIP, which is a serious shame since this would probably solve all my issues.

 

[Anifinity]

[deleted, see above]

 

[Nicklebon]

Accept as fact:

1. Only one NIC can have a default route
2. You will need to manually define static routes to direct traffic through the other NIC.

This means instead of setting the second router as a default route you define static routes to the networks you wished to attach to via the second NIC and point them to the second router instead of the default route.

Easy simple basic routing 101.

 

[Metraon]

It looks like Windows 8 does not support forcebindIP, which is a serious shame since this would probably solve all my issues.

Yep, I do think so. You could always contact the guy who wrote the code, prehaps he will be willing to give you the source and find a workaround !

Good luck !

 

[Anifinity]

Accept as fact:

1. Only one NIC can have a default route
2. You will need to manually define static routes to direct traffic through the other NIC.

This means instead of setting the second router as a default route you define static routes to the networks you wished to attach to via the second NIC and point them to the second router instead of the default route.

Easy simple basic routing 101.

I have no qualms about setting up routing, I simply want to know how I can do this seeing as the NIC's cannot see each other's subnet. How can I set a route from one NIC to another when they are not joined as part of a subnet? If you can give some instruction I am more than willing ti set this up.

 

[Nicklebon]

In reality the NICs are irrelevant. They simply establish the directly connected networks.

Thus the whole point of ....... wait for it .......... R O U T I N G


You will be making use of the CLI and the route command. Once you type in the route command you will see an example. I trust you can figure it out from there.

 

[Eickst]

Leave your primary adapter as DHCP.

Since your second adpater's cable connection is probably DHCP, you will need to set it up as a static IP using the address you received from DHCP. Use the same mask that you received from DHCP, but leave the gateway and DNS entries BLANK.

Open command prompt as administrator

Type in -

route add x.x.x.x mask 255.255.255.255 z.z.z.z -p

Where x.x.x.x is the ip address of the server that your application is connecting to and
z.z.z.z is the ip address of your cable modem. The -p means its a persistent route and will survive reboots.

Now when you open your browser, and go to msn.com, your computer's networking stack (not nic) will use the default gateway to send packets to. Any other website will use the default gateway. That's why its called a default. Any time your networking stack wants to send data to the x.x.x.x address that your application is connecting to, it will do so using the directly connected network. It doesn't try to use a gateway to connect to networks that you are directly connected to. I.E., your computer will never need to contact a gateway to send data to a machine on the 192.168.1.0 network because you are directly connected to it. Since you are directly connected to the subnet your cable modem is on, it will send info to x.x.x.x using the second NIC, it does NOT NEED TO CONTACT A GATEWAY!

 

[tporter]

This is based on saying you use the 2nd ISP only for a certain application...

Assuming both ISPs are using public dhcp, use 2 seperate routers with your 2 nics, with different private ranges i.e. 192.168.1.x, 192.168.2.x

Have your first nic dhcp or static with 1st router, and ONLY have DNS/GW on this nic (192.168.1.1). Default traffic and dns lookup will always go out this nic. (even when traffic goes out the second nic, using 1st nic dns servers is fine; also sometimes certain ISPs will block DNS lookup if it is not coming from their service, I.e. trying to do lookups on "internal" AT&T servers from you Comcast ip address)

Have your second nic assigned with JUST ip and mask, NOT with DNS or GW
Any traffic dedicated to second ISP - create a static route to public ip using 192.168.2.1 as route. Because routing tables shows 192.168.2.x as a local network of second nic, all traffic to that public ip will be routed out that isp