This article was previously published under Q198406
This article has been archived. It is offered "as is" and will no longer be updated.
Your Windows NT servers that are running the Routing and Remote AccessService (RRAS) Update are not advertising subnet routes for your IPnetworks. Instead, they are advertising one network route that summarizesthe missing subnets.
The Windows NT routers are using a feature known as subnet hiding.
To resolve this problem, obtain the latest service pack for Windows NT 4.0. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Windows NT version 4.0 Service Pack 5.
The feature described above, subnet hiding, is expected behavior with RIPversion 1. RIP version 1 does not have a field for the subnet mask of anetwork and does not support subnet advertisements. When advertising routesto an external network that could not possibly know the subnet mask, thesubnetted routes are reduced to a single network route or a Summary Route.
RIP version 2 is capable of advertising subnet masks; however, RIP version2 may not advertise specific subnet routes when RIP version 1 routers couldmistake the routes as host routes. This would be the case if the RIPversion 1 router had a different network ID than the RIP version 2 router.
This behavior of subnet hiding is always done with RIP version 1 and isusually done with RIP version 2. With some implementations of RIP version2, subnet hiding can be enabled or disabled.
If the announce mode is set to RIP1 or RIPv2 broadcast the subnet summarization (hiding) is always performed. You must choose RIPv2 multicast mode to disable subnet summarization.
Also, the RRAS command-line utility can be used to turn this feature on or off. The following syntax example is provided:
routemon ip set protocol[proto=] rip[name=] <interface-name>[subnetsummary=] <enable|disable>]