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Configuring IP Routing

After you have your server’s network interfaces configured with the appropriate IP addresses and RRAS is enabled, you can configure the server for routing IP. Routing can be handled in two different ways: static routing and dynamic routing.

As already mentioned earlier in the hour, static routing requires that routing information be entered by the administrator. The static route is fixed and cannot react to changes in the network topology.

Dynamic routing uses a routing protocol that builds and maintains the routing tables. The routing tables determine how data is then routed on the network. Windows Server 2008 uses RIP (Routing Information Protocol) as the routing protocol.

Let’s take a look at how to configure static routing. We can then take a look at the alternative, dynamic routing, and look at how to add RIP to the RRAS configuration.

Configuring Static Routing

Static routing is configured in the RRAS snap-in. A static route configuration consists of an interface selection (one of the network interfaces on the routing server), a destination address, a gateway, and a metric.

In terms of routing, the gateway is the address of the device that provides the connection between the networks that will embrace the static route that you are creating. The gateway basically functions as a forwarding agent as the packets move to their final destination.

A metric is the number of hops (from router to router) that are required to move the packets from source to destination. You want to create routes with the fewest number of hops (also known as the cost of the route) and, thus, the lowest metric.

To configure a static route, follow these steps:

1. Expand the server node in the RRAS snap-in tree in the MMC (or the Routing and Remote Access node in the Server Manager). Then expand the appropriate IP routing node. (Because IPv4 routing is much more common than IPv6 routing, expand the IPv4 node.)

2. Right-click the Static Routes node, and select New Static Route. The Static Route dialog box appears (see Figure 18.7).

Figure 18.7. The Static Route dialog box.

3. Use the Interface drop-down list to select the interface on the router (the RRAS server) that you want to configure with the static route.

4. Enter the destination IP address in the Destination box.

5. Enter the network mask (the net mask that you computed when you subnetted your network—this is discussed in Hour 7) for your network. If you want to make the route proprietary for packets with the destination address that you entered in the Destination box, use the mask of 255.255.2555.255. If you want to make the route available for any destination, enter the mask of

6. In the Gateway box, enter the IP address of the forwarder for your network segment.

7. Enter the metric for the route in the Metric spin box. The default is the maximum 256.

8. Click OK to complete the creation of the static route.

Other static routes can be created as needed. You can edit any static route by right-clicking the route in the Details pane and then selecting Properties. Delete static routes by right-clicking the route and then selecting Delete.

If the number of hops or other network topology changes in relation to your static routes, you must reconfigure the routes. Because static routes are static (and require hands-on editing and management), the alternative of dynamic routing might be more to your liking. Dynamic routing is discussed in the next section.

Did you Know?

You can also create static routes at the command line by using the route command. Use the route print command to view the routing table.

Configuring Dynamic Routing

To configure dynamic routing, you must add the RIP routing protocol to the IP (routing) node of your server/router. RIP is a distance-vector routing protocol that uses hop count as its metric. RIP sends out routing update messages every 30 seconds to neighboring routers. Because RIP is a distance-vector routing protocol, it requires routers to share complete copies of their routing tables with other routers. RIP has a limit of 15 hops and, thus, is not appropriate for very large enterprise-size internetworks.

By the Way

Windows Server 2003, the previous version of Microsoft’s network OS, also provided a second routing protocol OSPF (Open Shortest Path First) as an RRAS option and alternative to RIP. OSPF has been removed from the Windows Server 2008 RRAS configuration, so RIP is the only possibility.

To add RIP to your server/router, follow these steps:

1. Expand an IP node in the snap-in tree (such as the IPv4 node).

2. Right-click the General node and select New Routing Protocol from the shortcut menu. The New Routing Protocol dialog box opens (see Figure 18.8).

Figure 18.8. Adding a routing protocol.

3. Select RIP Version 2 for Internet Protocol (the DHCP Relay Agent choice is discussed later in the hour).

4. After selecting RIP, click OK. RIP is added to the IP node as a subnode.

After you’ve added RIP to the RRAS IP Routing configuration, you need to create an interface for the routing protocol. Configuring RIP interfaces is discussed in the next section.

By the Way

Adding RIP to the IPv4 node does not automatically add RIP to the IPv6 node. So, if you are planning on routing IPv6 addresses, you need to add RIP to IPv6 as well.

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