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Demand-dial routing updates

  • Article

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Demand-dial routing updates

While demand-dial routing can save connection costs, typical routing protocols rely on a periodic advertising process to communicate routing information. For example, RIP for IP advertises the contents of its routing table every 30 seconds on all interfaces. This behavior is not a problem for permanently connected LAN or WAN lines. For usage-sensitive dial-up WAN lines, this type of periodic behavior could cause the router to call another router every 30 seconds, which may result in an undesirable phone bill. Therefore, you should not run routing protocols across temporary dial-up WAN lines.

If you do not use routing protocols to update the routing tables, then you must enter the routes as static routes. The static routes that correspond to the network IDs available across the interface are entered manually or automatically. The automatic entering of static routes for demand-dial interfaces is known as auto-static updates and is supported by the server running Routing and Remote Access. Auto-static updates are supported when you use RIP for IP, but not OSPF.

When instructed, a demand-dial interface that is configured for auto-static updates sends a request across an active connection to request all of the routes of the router on the other side of the connection. In response to the request, all of the routes of the requested router are automatically entered as static routes in the routing table of the requesting router. The static routes are persistent; they are kept in the routing table even if the interface becomes disconnected or the router is restarted. An auto-static update is a one-time, one-way exchange of routing information.

You can automate and schedule auto-static updates by executing the update as a scheduled task. For more information, see Scheduling auto-static updates.

Notes

  • The "auto" in auto-static refers to the automatic adding of the requested routes as static routes in the routing table. The sending of the request for routes is performed through an explicit action: either through Routing and Remote Access or the Netsh utility while the demand-dial interface is in a connected state. Auto-static updates are not automatically performed every time a demand-dial connection is made.

  • When an auto-static update is requested, the existing auto-static routes are deleted before the update is requested from other routers. If there is no response to the request, then the router cannot replace the routes it has deleted. This may lead to a loss of connectivity to remote networks.

  • Open Shortest Path First (OSPF) is not available on Windows XP 64-bit Edition (Itanium) and the 64-bit versions of the Windows Server 2003 family.