Routing Information Protocol (RIP) 299Route Aggregation Route aggregation mode determines which route table entries are sentduring a RIP-2 update:n If route aggregation mode is enabled, RIP-2 can function like RIP-1and “collapse” route table entries for all subnets of a directlyconnected network.For example, if route aggregation is enabled, and the system isadvertising subnets 150.100.31.0 and 150.100.32.0, only the entryfor network 150.100.0.0 is sent in the update. With RIP Version 2, youmust enable route aggregation mode if you want the interface tocollapse the route table entries and function like RIP-1.n If route aggregation mode is disabled (the default), a RIP-2 updatesends all routing table entries.RIP-1 Versus RIP-2 Like RIP-1, RIP-2 allows the system to dynamically configure its ownrouting table. RIP-2 is much more flexible and efficient than RIP-1,however, because RIP-2 advertises using the multicast method, which canadvertise to a subset of the network (RIP-1 uses the broadcast method,which advertises to the whole network). RIP-2 can do this because itincludes a subnet mask in its header. (See Figure 59.)If your system receives a RIP-2 packet, your system puts the route into therouting table with the subnet mask that was advertised.Figure 59 RIP-1 Versus RIP-2Gateway address158.101.1.253(255.255.255.0)How IP address 158.101.5.1goes into the routing table ofSystem B:RIP-1 158.101.0.0RIP-2 158.101.5.0Gateway address158.101.1.254(255.255.255.0)158.101.5.1(255.255.255.0)System ASystem B
