Consider the following scenario:

  • Lots of IP addresses are assigned to one network adapter on a computer that is running Windows Server 2008 Service Pack 2 (SP2) or Windows Vista Service Pack 2 (SP2).
  • Only the primary IP address is used for outgoing traffic.

In this scenario, only the primary IP address should be registered on the DNS servers for outgoing communication purpose. However, all IP addresses are registered on the DNS servers.

The issue causes the following symptoms:

  • The communication to the computer is blocked by a firewall. Because all IP addresses are registered on the DNS servers, all these IP addresses seem to be valid IP addresses that can be used to communicate with the computer. However, if only the primary IP address can pass through a firewall, communication that uses all other IP addresses is block by the firewall.
  • A large amount of DNS registration traffic and a large amount of update traffic is generated. However, this traffic is unnecessary because these IP addresses are not used for outgoing traffic.

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