FIX: Cannot Renew DHCP Assigned IP Address on External ISA Interface

On a computer running Internet Security and Acceleration Server, where the external interface is configured to have its IP address dynamically assigned from DHCP, you may not be able to renew the IP address on the interface.

For example, if you run ipconfig /release, followed by ipconfig /renew, from a command prompt, you may receive an error message similar to the following: Additionally, you may not be able to turn off and turn on the external network adapter, or to automatically or manually change the assigned IP address on the external network adapter in ISA Server.

This problem also occurs when you have the DHCP Client Static Packet filter turned on in ISA Server.

The only way to renew the IP address is to temporarily turn off packet filtering or restart the computer running ISA Server.

The DHCP Client Static Packet filter only permits you to refresh the already assigned external IP address.

For example, when the DHCP lease has expired and the IP address on the external interface is lost or manually released, a renew of the IP address is blocked by the ISA Server Packet Filter module. The ISA service is not fully Plug and Play when the IP address is released on the external interface. Therefore, packet filtering is still applied to the interface.

You must install ISA Server Service Pack 1 (SP1) before you install the following hotfix. For additional information about how to obtain the latest ISA Server service pack, click the article number below to view the article in the Microsoft Knowledge Base: A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language. To install the fix, run the self-extracting file. You do not have to restart the ISA Server computer. If the computer is part of an ISA Server array, you do not have to shut down the whole array. You can still install this fix on a one-by-one basis.

The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel. This fix also applies to the French, German, Spanish, and Japanese versions of ISA Server.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

Note that after you install this hotfix, while you are renewing the DHCP assigned IP address, you may receive an event notice in the Application Event Log similar to the following: The following information is part of the event: When you release the DHCP assigned IP address, you may also receive an event message similar to the following: For example, this event may appear in the log if the packet filter is currently handling a packet. While you change the IP address on the external adapter, this causes routing table changes in the operating system (OS). Because ISA Server does spoof detection by comparing the interface on which the packet was received to the interface from which a reply to the originating source would be sent, it would consider this to be a spoofed packet if the two interfaces are different.

The following is still not supported after you install this hotfix:

• If you change the IP address on the internal network adapter, SecureNAT stops functioning.
  
  NOTE: Such changes are rare because in a SecureNAT scenario, the internal IP address of the ISA Server computer should never use DHCP, which must be configured as a gateway on the router or on all computers in the local internal subnet.
• Dynamic filters for listeners that bind to IP 0.0.0.0 are not opened in the following scenarios:
  • A new external IP is added after the filters for the listener were created.
  • An external network adapter that is not a Routing and Remote Access service demand-dial (that existed when dynamic filters for the listener were created) is turned off, and receives a new IP when it is turned on. The only ISA application filter that opens the listener is the H.323 filter, which opens TCP port 1720 for incoming calls.
• Local Address Table (LAT) changes that change the status of a network adapter from external to internal, or from internal to external, are not supported. In this case, ISA Management also prompts you to restart the ISA services.