Nat – Windows Server 2008: specifying the default IP address when NIC has multiple addresses

ip addressnat;networkingnicwindows-server-2008

I have a Windows Server which has ~10 IP addresses statically bound. The problem is I don't know how to specify the default IP address.

Sometimes when I assign a new address to the NIC, the default IP address changes with the last IP entered in the advanced IP configuration on the NIC. This has the effect (since I use NAT) that the outgoing public IP changes too.

Even though this problem is currently on Windows Server 2008.

How can you set the default IP address on a NIC when it has multiple IP addresses bound?

There is more explication on my problem.

alt text http://www.nmediasolutions.com/_images/probleme/ip.png

Here is the output of ipconfig:

DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
IPv4 Address. . . . . . . . . . . : 192.168.99.49(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.51(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.52(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.53(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.54(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.55(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.56(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.57(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.58(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.59(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.60(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.61(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.62(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.64(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.65(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.66(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.67(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.68(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.70(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.71(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.100(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.108(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.109(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.112(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
IPv4 Address. . . . . . . . . . . : 192.168.99.63(Duplicate)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.99.1

If I do a pathping there is the answer, the first up is the 99.49, also if my default IP address is 99.100

Tracing route to www.l.google.com [72.14.204.99]
over a maximum of 30 hops:
  0  Machine [192.168.99.49]

There is the routing table on the machine:

 Network Destination        Netmask          Gateway       Interface  Metric
              0.0.0.0          0.0.0.0     192.168.99.1    192.168.99.49    261
           10.10.10.0    255.255.255.0         On-link       10.10.10.10    261
          10.10.10.10  255.255.255.255         On-link       10.10.10.10    261
         10.10.10.255  255.255.255.255         On-link       10.10.10.10    261
         192.168.99.0    255.255.255.0         On-link     192.168.99.49    261
        192.168.99.49  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.51  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.52  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.53  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.54  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.55  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.56  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.57  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.58  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.59  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.60  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.61  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.62  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.64  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.65  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.66  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.67  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.68  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.70  255.255.255.255         On-link     192.168.99.49    261
        192.168.99.71  255.255.255.255         On-link     192.168.99.49    261
       192.168.99.100  255.255.255.255         On-link     192.168.99.49    261
       192.168.99.108  255.255.255.255         On-link     192.168.99.49    261
       192.168.99.109  255.255.255.255         On-link     192.168.99.49    261
       192.168.99.112  255.255.255.255         On-link     192.168.99.49    261
       192.168.99.255  255.255.255.255         On-link     192.168.99.49    261
            224.0.0.0        240.0.0.0         On-link     192.168.99.49    261
            224.0.0.0        240.0.0.0         On-link       10.10.10.10    261
      255.255.255.255  255.255.255.255         On-link     192.168.99.49    261
      255.255.255.255  255.255.255.255         On-link       10.10.10.10    261

I think my route should look like:

Network Destination        Netmask          Gateway       Interface  Metric
              0.0.0.0          0.0.0.0     192.168.99.1    **192.168.99.100**    261
           10.10.10.0    255.255.255.0         On-link       10.10.10.10    261
          10.10.10.10  255.255.255.255         On-link       10.10.10.10    261
         10.10.10.255  255.255.255.255         On-link       10.10.10.10    261
         192.168.99.0    255.255.255.0         On-link     192.168.99.100    261
        192.168.99.49  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.51  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.52  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.53  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.54  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.55  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.56  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.57  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.58  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.59  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.60  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.61  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.62  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.64  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.65  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.66  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.67  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.68  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.70  255.255.255.255         On-link     192.168.99.100    261
        192.168.99.71  255.255.255.255         On-link     192.168.99.100    261
       192.168.99.100  255.255.255.255         On-link     192.168.99.100    261
       192.168.99.108  255.255.255.255         On-link     192.168.99.100    261
       192.168.99.109  255.255.255.255         On-link     192.168.99.100    261
       192.168.99.112  255.255.255.255         On-link     192.168.99.100    261
       192.168.99.255  255.255.255.255         On-link     192.168.99.100    261
            224.0.0.0        240.0.0.0         On-link     192.168.99.100    261
            224.0.0.0        240.0.0.0         On-link       10.10.10.10    261
      255.255.255.255  255.255.255.255         On-link     192.168.99.100    261
      255.255.255.255  255.255.255.255         On-link       10.10.10.10    261

How can I be sure the IP address used in the image (supposed to be the default IP address) will be use by my server as the default address?

Best Answer

With Server 2008 Service Pack 2 (not R2), or Vista SP2 and MS hotfix KB975808 there is a solution, although a bit clumsy. You would remove all the addresses you DON'T want as a source, then re-add each one at the command line using

Netsh int ipv4 add address <Interface Name> <ip address> skipassource=true

The hotfix enables the "Skip As Source" flag.

For a deeper dive on how different Windows versions select source IPs, see this TechNet blog post.

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