ccna security lab 9.3.1.1 pdf

ccna security lab 9.3.1.1 pdf.will automatically summarize any routing information; therefore, when using OSPF, you must manually configure the classification map 7.9 Classification and routing updates for classless protocolsGiven the behavior of classified routing protocols, some addressing schemes can cause problems. See the network shown in the ± half of Figure 7.10. When using a classification protocol (such as RIPV1), routers located on the boundary of the classification network will aggregate subnets into the classification network. In this example, Router A and Router B both advertise 172.16.0.0, but not the subnets in 172.16.0.0. This confuses Router C because it receives two routes to 172.16.0.0. If Router C wants to send a packet to 172.16.1.0/24, it will not know which router it should send it to (Router A or Router B).The reality is a little more complicated than that. With a basic RIP implementation, Router C will add the last received route to the routing table.172.16.1.0/24 -------------------.and then forwards the packet out the interface connected to the appropriate router. There is a 50/50 chance that the packet will be forwarded to both Router A and Router B, depending on which router Router C last received the routing update from. However, if the routing protocol used is EIGRP, the metric will result in one route being preferred over another, and all packets will be forwarded based on the route with the smaller metric.192.168.1.0/24This design is called a subnet separation design.This design is called a subnet separation design-not all subnets are connected together. In this network, subnets 172.16.1.0/24 and 172.16.2.0/24 are not connected together, which creates routing problems for routers that are not in network 172.16.0.0, so a subnet-separated design is not recommended when using a classful protocol.However, classless protocols support subnet separation. As shown in the bottom half of Figure 7.10, the routing updates for classless protocols include subnet masks. In this example, Router C knows the exact location of 172.16.1.0/24 and 172.16.2.0/24 because the routing update contains the subnet mask.However, even if you are using a classless protocol, it is not recommended to use a subnet separation design because it will not allow you to aggregate routing information most efficiently. Routing protocols and the creation of routing tables are discussed in Chapters 14, 18, 19, and 20. For now, you just need to keep the following key point in mind: on classified network boundaries, the classification protocol always advertises the classified network number.