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Missing Default Gateway?

By baird.jason ·
Good morning all,

I have an odd issue I am hoping someone can help me with.

I have a Windows 2003 terminal server with 2 NICs that are both on the same subnet of 10.180.x.x. They have the same Subnet Mask and Default Gateway. One card is configuring for Internal use and one for External (just to make firewall rules easier for our setup). Occassionally the Default gateway for the Internal card disappears from the ipconfig listing. The other card is fine. If I drop to a command prompt and run an "ipconfig /registerdns" the issue is resolved and the Gateway shows up again or if I do a repair on the card it also resolves the issue. Sometimes it occurs every morning and other times it could be a week or two before it shows up again.

I have tried updating the NIC drivers, server firmware, triple checked the DNS configuration and tried resetting the TCP/IP stack using the netsh command. Anyone have any ideas or suggestions?

Jason

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All Answers

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Dead Gateway Detection

by robo_dev In reply to Missing Default Gateway?

Windows 2003 has a feature called 'dead gateway detection' that will remove the slower (presumably) dead gateway.

http://msdn.microsoft.com/en-us/library/aa505956.aspx

In order to fix this, you may need to fiddle with the routing metric for each interface, otherwise windows will pick what it sees as the faster interface, or even pick the first one in the binding order....

http://technet.microsoft.com/en-us/library/cc779696%28WS.10%29.aspx

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Reponse To Answer

by baird.jason In reply to Dead Gateway Detection

Will this work if the two nics have the same gateway?

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To get into the bytes and bits of it

by robo_dev In reply to Missing Default Gateway?

since your server, as configured, is routing between the two interfaces, it really can only have one 'default gateway', to allow any connected devices to reach the outside network, since there can be only one valid route at a time. The fact that the two default gateways are the same does not matter (it's not that smart). Windows is making a routing decision based on which interface looks to be faster.

I think what you really want to do is 'NIC Teaming' at the driver level (lots of Intel server NICS do this). This allows two NICs to appear as one, from a TCP/IP and routing perspective, while giving you the option of making the link fault tolerant and/or aggregating the bandwidth of the two interfaces.

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You are doing it wrong

by Spitfire_Sysop In reply to Missing Default Gateway?

Let's be clear. There is only one default gateway on one NIC: The external NIC.

If you have 2 NICs in the same subnet then they are both internal by definition. They are both in your internal intranet. External usually refers to the internet or a different subnet. If they are both on the same subnet you would need to do load balancing to make it use both. I think by default it will use one and failover to the other to avoid confusing itself.

If you are setting different firewall rules on the different NICs you may not be getting the desired results. For example if a connection is blocked at one NIC what is stopping that connection from entering through the other NIC with different rules? They both map to the same DNS entry...

If you are using your Win2k3 server as a firewall inbetween your border device and your LAN device (don't do this) then there are physical restrictions, being that the data must flow through your server to get on to the LAN. If this is the case you need to enable routing on your server and set the two NICs in different subnets. Even if there is a subnet containing only 2 devices: The border router and the server. It's a simple fix.

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Reponse To Answer

by baird.jason In reply to You are doing it wrong

Actually, I have discovered the only reason we use the 2 NICs is for allowing us to RDP in. Not fulling uderstanding why it's done but I inherited it. It's not Firewall based at all. The interesting thing I find is that itly happens occassionally and users cannot access the Internet until I run a NIC repair or simply run the ipconfig /registerdns command.

J

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