Updating to WinNT 3.51 SP2 Causes Loss of Persistent IP Routes (138995)

SYMPTOMS

You added persistent IP routes with the "route" command. After applying Windows NT 3.51 U.S. Service Pack 2, the routes no longer appear in the route table. Connectivity that relies on those routes does not function properly.

CAUSE

An enhancement was made to the route command for Windows NT 3.51 Service Pack 2 to allow a metric (hop count) to be specified. This hop count parameter is stored in the registry along with the other information for each persistent route. The route entry format was changed in the registry to add a field for the metric, and the new route code can not read the older-style entries.

WORKAROUND

There are currently three ways to regain the previous routes. Two require the use of Regedt32.exe to modify the registry:

Delete the registry values for the old persistent routes, and re-add the routes using the route /p command:

ROUTE -p add [destination] [MASK netmask] [gateway] [METRIC metric]]

-or-
Modify the old registry values by adding the metric to them. They will then become visible after the next reboot.

-or-

Upgrade to Windows NT 4.0 Server or Workstation which will recognize and update the 3.51 route format by applying a default metric of 1.

MORE INFORMATION

In Windows NT 3.51, the ROUTE.EXE command can store persistent IP routes as values under the following registry key:

HKEY_LOCAL_MACHINE
\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Persistent Routes

Each route is stored in the value name string as a comma-delimited list of the form:

destination,subnet mask,gateway

For example, the value representing a host route to destination 45.100.23.10 through gateway 131.110.0.1 would be named:

45.100.23.10,255.255.255.255,131.110.0.1

The value type is a REG_SZ. There is no value data (empty string).

After applying Service Pack 2, the expected format changes to:

destination,subnet mask,gateway,metric

The sample entry above could be modified as follows:

   45.100.23.10,255.255.255.255,131.110.0.1,1
                                            ^ a metric of "one"

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 3.51. This problem was corrected in the latest Windows NT 3.51 U.S. Service Pack. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K