KB169417 - RAS Clients Are Unable to Access All Networks in an OSPF Network

Article ID: 169417

Article Last Modified on 10/31/2006

Microsoft Windows NT Server 4.0 Standard Edition
Microsoft Routing and Remote Access Service Update for Windows NT Server 4.0

This article was previously published under Q169417

SUMMARY

If they are not configured properly, Remote Access Service (RAS) clients may not have full network access when the RAS server is also an OSPF router. This will only occur if OSPF is not properly configured and the RAS IP address pool does not match the IP subnet of a LAN interface. Loss of connectivity for LAN clients can also result if OSPF is not properly configured.

MORE INFORMATION

On an OSPF router, OSPF must be running for that interface to be included in OSPF link state advertisements. In other words, if a particular interface is not running OSPF, it is considered external and the route to this network will not be advertised. RAS interfaces, as well as LAN interfaces, can be considered external to OSPF. If RAS is using a pool of IP addresses from a unique subnet, then a route to this subnet needs to be advertised.

You will need to make this OSPF router an Autonomous System (AS) boundary router (ASBR). Enabling this feature tells the router to advertise external routes to the rest of the OSPF network. To enable this functionality, right-click OSPF, click Configure OSPF By Bay Networks, and then select the Enable Autonomous System Boundary Router check box.

When a router is an ASBR, it will advertise all routes including the default gateway. For additional information, please see the following article in the Microsoft Knowledge Base:

166170 Using Default Gateways with OSPF

If RAS is using a pool of addresses that are within the same subnet as one of the routers' OSPF interfaces, or you are using DHCP for the RAS address pool, you need not do anything. In this case, the subnet is already being advertised and RAS will use Proxy ARP to get packets to the RAS clients.

Additional query words: rras

Keywords: kbnetwork KB169417