Since static routing can become cumbersome in very large internetworks, companies will usually choose to have routing tables built dynamically by a routing protocol. It is via routing protocols that routers ‘talk’ to one another, exchanging information about the networks that they are aware of. Although a wide variety of routing protocols exist, Windows 2000 supports only three, RIP versions 1 and 2, as well as OSPF. In order for routers to exchange information with one another, they must be running a common routing protocol. By far the simplest routing protocol to implement is RIP, the Routing Information Protocol. RIP’s simplicity comes from the fact that it requires very little in terms of configuration outside of simply ‘turning it on’. In an internetwork that uses RIP, routers broadcast their routing tables to their neighbors at configurable intervals. The downside of this is that it has a negative impact on network performance, and changes in the network topology (such as a router going down) can take a long time to propagate through a network, thus compounding network communication problems.
As mentioned earlier, Windows 2000 supports both RIP versions 1 and 2. RIP version 1 is often considered a poor choice in larger environments, mainly because it only supports classful IP addressing, which in part means that subnet mask information is not propagated as part of the RIP v1 broadcasts. This also means that RIP version 1 is not suitable for networks that use either CIDR (classless interdomain routing) or VLSM (variable-length subnet masks). Another downfall of RIP v1 is the fact the security is very limited, since neighboring routers do not authenticate with one another. This would might allow any RIP router to exchange information with neighboring RIP routers, regardless of whether they should be.
On the other hand, RIP version 2 does support VLSM, CIDR, and basic authentication (a string value that must be the same on routers participating in the exchange, via clear text). RIP v2 routers also support the exchange of information via broadcast or multicast, which can be configured. Note that a router running only RIP v1 cannot exchange information with a router running only RIP v2.
RIP is added via the ‘New Routing Protocol’ menu choice off the General tab in the IP Routing section of Routing and Remote Access.
Note that you first add a routing protocol, and then configure that protocol on an interface-by-interface basis. Note also that even though the screen above suggests that only RIP version 2 can be added, this option also allows you to configure interfaces using RIP 1 if desired.
By accessing the properties of RIP via the shortcut menu, you are actually configuring what are sometimes referred to as global parameters. The options here are limited, since an interface hasn’t actually been added yet, as will be discussed in a moment. The general tab controls how long a router will wait before sending a triggered update (meaning that its table has been updated), as well as RIP logging options. The Security tab is actually a little more important, since it allows you to control exactly which RIP routers this router is allowed to interact with. While the router will be able to accept announcements from all other RIP routers (running the same version) by default, you can also specify which routers it can or cannot accept announcements from explicitly by IP address.