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Multiple NIC's - Ping responds with IPv6

Posted on 2011-03-03
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Last Modified: 2012-06-21
Hi Experts,

I have a faew servers all hosted at a local datacenter. Each server has 3 NIC's installed. Each server has a NIC for the backup network at the datacenter, a NIC for accessing the public internet and the third NIC is for a private network. On the Microsoft SQL server, we do not have the NIC with public internet access enabled, so it access the other servers via the private network, 10.0.0.X

When I ping from server1 to the SQL server, it responds with a IPv6 address. Ultimately, I am trying to resolve this issues so they respond via IPv4. On the SQL server, it seems if all traffic is being routed out the backup network NIC and not the private network NIC as it should be. If I disable the backup network NIC and only have the private NIC enabled, I can no longer RDP between servers and they don't respond to any ping request. I've even added the private addresses to the host file and no luck. I've also disabled IPv6 in the private NIC on all servers.
Is there a way to say which NIC the server should use first?

Thanks!
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Question by:RLComputing
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OrcaKnight earned 125 total points
ID: 35029593
Typically, the ROUTE ADD command is used to specify which interface to send a IP request out of, if that routed network is not on the default NIC/gateway. In order to determine your issue better, we need the NIC subnets and masks, as well as a bit of info on the network topology. Is the backup network on completely isolated VLANs or network hardware? Is the primary and backup in the same subnet?
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by:RLComputing
ID: 35029848
The private NIC subnet is 255.255.255.255
The backup NIC subnet is255.255.255.0
The internet access NIC subnet is 255.255.255.0

I believe the backup network is on a separate VLAN but will have to double check with my data center.
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Assisted Solution

by:IPv6Guy
IPv6Guy earned 125 total points
ID: 35030270
Try doing a tracert instead of a ping; that should verify which interface is being used for the request.

It is normal for two Windows machines on the same subnet to respond with an IPv6 address. If you want to force IPv4, try using the -4 switch, like this:

ping -4 server1
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by:RLComputing
ID: 35030603
the server will respond with the ping -4 but when I do a tracert it is routing out the public internet NIC, which would explain why it can't connect to the server. Is there a way to change which NIC it can route of?

I did read up on the ROUTE ADD command however we don't have a gateway for the private NIC so I was unable to add a manual route.
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Expert Comment

by:IPv6Guy
ID: 35030931
Can you please provide the IP address of the SQL server, and the results of ROUTE PRINT from one of the servers you are trying to ping from?
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by:RLComputing
ID: 35031225
I was able to resolve the issue with the Route Add command.
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by:RLComputing
ID: 35031238
In case anyone else needs it for future reference. It routes all private requests out the private NIC gateway.

route add 10.0.0.0 mask 255.255.255.0 10.0.0.4
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