Windows XP incorrectly forwards UDP broadcast packets (835979)
The information in this article applies to:
- Microsoft Windows XP Professional
- Microsoft Windows XP Home Edition
SYMPTOMSA multi-homed Microsoft Windows XP-based computer may not
correctly forward User Datagram Protocol (UDP) broadcast packets from one
subnet to another. Additionally, the multi-homed Windows XP-based computer may
not process the UDP packet if a program or Windows XP is listening for that
particular broadcast packet.CAUSEThis issue may occur if you use an IP address from one class
and a subnet mask from another class, such as such as a Class A network IP
address with a Class C subnet mask.
For example, suppose a Windows
XP-based multi-homed computer has a Class A network IP address of 10.0.0.1 and
a Class C subnet mask of 255.255.255.0. In this configuration, the computer
performs a subnet broadcast to the IP address 10.0.0.255. The packet-forwarding
mechanism that Windows XP uses incorrectly assumes that this packet must be
sent to a valid host computer and not to a subnet broadcast. Windows XP makes
this supposition because the subnet mask is not consistent with the class A
address.
Therefore, the packet will be incorrectly forwarded, but
the packet will not be sent to the TCP/IP stack of the computer that does the
forwarding. WORKAROUNDTo work around this problem and to correctly forward and
route UDP broadcast packets from one subnet to another, you must configure the
multi-homed Windows XP-based computer as a dedicated UDP router.STATUSMicrosoft
has confirmed that this is a problem in the Microsoft products that are listed
in the "Applies to" section.
| Modification Type: | Minor | Last Reviewed: | 1/27/2005 |
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| Keywords: | kbtshoot kbnofix kbbug KB835979 kbAudITPRO |
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