RIP Version

RIPv2 enhances the original RIP packet with the addition of a network mask field and a "next hop address" field. The network mask is the bit mask that is used to determine the destination network. Sending the mask with the destination address in the routing update is an essential component of classless IP addresses.

To make your network masks globally available, they must be distributed to other systems. The routing protocol is used to do this, and RIPv2 adds this capability to RIP.

The "next hop address" field provides the address of the gateway. In RIP, only the destination address and the metric are provided. The gateway is always assumed to be the router that sends out the update. The next hop address field specifically provides the address of the gateway, which allows the system that sends the update to be different from the gateway that will handle the route. Thus, RIPv2-capable systems can provide updates for routers that don't run RIPv2. If the next hop address is 0.0.0.0, the router that sends the update is assumed to be the gateway for the route.

In addition to these enhancements that address the biggest problem with RIP, RIPv2 adds a few nice features:

• RIPv2 is completely compatible with RIP because the RIP packet format is unchanged. All of the features of RIPv2 are implemented in unused fields of the original RIP packet. RIP and RIPv2 routers can coexist on a single network without a problem.

• RIPv2 uses multicasting instead of broadcasting to reduce the load on systems that do not want RIPv2 updates.

• RIPv2 provides an authentication scheme that prevents routing updates from a misconfigured host from accidentally being accepted as valid.

Despite its improvements, RIPv2 is still RIP. Therefore, it uses the same distance-vector algorithm for determining the best route, and it limits the diameter of the network to 15 hops. OSPF, a different type of interior protocol, was developed for very large national networks.

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