Microsoft KB Archive/235489

= How to Use Routing Information Protocol Over Routing and Remote Access Service Dial On Demand and Virtual Private Network Connections =

Article ID: 235489

Article Last Modified on 11/1/2006

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APPLIES TO


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

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This article was previously published under Q235489



SUMMARY
This article describes how to implement Routing Information Protocol (RIP) over Routing and Remote Access Service (RRAS) Dial On Demand (DOD) connections. The implementation of this protocol is the same for both direct-dial modem connections and Virtual Private Network (VPN) connections over the Internet.



MORE INFORMATION
The information in this article applies to both direct connections and VPN connections. In the following examples, RRAS is used to provide LAN-to-LAN routing:

Example Direct-Dial Modem Connection

Lclient          L-RRAS === Modem === R-RRAS           Rclient |     IP      |                        |      IP      | --                         --

Example VPN Connection Lclient          L-RRAS ===== VPN ===== R-RRAS           Rclient |     IP      |  |      Internet     |  |      IP      | --   ---    --

NOTE: For the purposes of this article, a DOD connection refers to either a direct-dial connection using a modem or a VPN tunnel connection over the Internet. Because RIP does not distinguish between connectivity methods, both are used in the same manner.

Before you configure RIP for LAN-to-LAN routing (as in the two examples above), do the following:  Make sure your DOD connections dial and connect successfully.

This is true for both modem and VPN connections. You can add temporary static routes to the RRAS servers to test routing capabilities, but you should remove them after testing. RIP does not work if the DOD connections do not connect. Adding RIP from within the RRAS Management Console:  Start the RRAS Administration tool. In the IP Routing section, right-click Summary, and then click Add Routing Protocol. Click RIP version 2 for Internet Protocol, and then click OK.</ol> </li></ol>

During RIP installation, you can configure event logging on the General tab and security parameters on the Security tab. You should leave these set to their defaults during installation and change them after RIP is installed.

After you install RIP, the RIP for Internet Protocol icon is displayed in the IP Routing section of the RRAS Administration tool. Right-click RIP for Internet Protocol, and then click Add. Click the DOD interface you are using between the two RRAS servers (you need to do this on both RRAS servers). Add the interfaces that RIP uses in this section (usually the DOD interfaces and the LAN side interfaces). In the VPN example above, it is not necessary to add the interface that connects to the Internet unless there are other compelling reasons to do so.

When you add an interface, you can change the RIP configuration. Four tabs are available: General, Security, Neighbors, and Advanced. Typically, you can leave these settings at their default values and RIP functions properly. You can make any changes to RIP after you initially configure the added interfaces. The General tab is described in more detail below. For more information about these settings, refer to the RRAS Administrators Guide.

On the General tab, you can click Operation mode and choose one of the following options to indicate whether the interface is treated as a persistent connection or DOD connection:
 * Periodic Mode: Indicates that RIP broadcasts or multicasts are sent over the interface based on the periodic rate (the default setting is every 30 seconds).
 * Auto-Static Mode: Indicates that periodic updates are not sent over the interface and that manual updates by an administrator are necessary.

NOTE: By default, network adapters use Periodic mode, and DOD connections use Auto-Static mode, but you can specify the appropriate mode for your environment.

At this point, even though RIP is installed, DOD connections do not dial and cannot be forced to dial. Even if you configure the DOD connection to use Periodic mode, the connection does not dial. However, if you manually dial the connection and Periodic mode is enabled, the connection does not disconnect after connected. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

235492 RIP and OSPF Do Not Start Dial On Demand Connections

To force RIP to start a DOD connection, make sure that a route entry exists that forces the DOD connection to dial. You can do this using the appropriate method:

Using Auto-Static Mode
On each RRAS server in the IP Routing section, right-click the DOD (either the modem or VPN interface), and then click Update Routes. After the connection is made, the DOD copies over the routes normally learned by RIP as static routes in the route table. After this task is finished, the DOD is forced to dial back based on the routing table (even if the DOD drops because of inactivity). You must do this on each side, unless only one side is required to dial. These auto-static updates are not dynamic. If there are changes to a network, then you must select the Update Routes option again to update the static routes in the route table of the RRAS server. You may also need to stop and restart the RRAS server to complete the configuration changes.

Using Periodic Mode
Add a default gateway static route that points to the DOD or specific network routes that point to the DOD. You need to do this on each side for routing purposes. In this example, you must manually add the static routes and RIP learned routes are placed in the routing table after the DOD is connected. If you add static routes using Periodic mode, you should also do the following: <ol> Give static routes a higher metric than routes that are learned by RIP. This process is sometimes a matter of trial and error, but the desired result is that RIP learned routes have a better metric than the static routes.</li> Change the preference level of RIP routes: <ol style="list-style-type: lower-alpha;"> Start the RRAS Administration tool.</li> In the IP Routing section, right-click Summary, and then click Configure IP parameters.</li> On the Preference Levels tab, click RIP Version 2 for Internet Protocol, and change the preference level from 4 to 1 (the preference level itself is not as important as the fact that you should give RIP routes more preference than static routes).</li></ol> </li></ol>

Keywords: kbenv kbinfo KB235489

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