the routes as seen in R2: 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks 10.0.0.0/8 [90/30720] via 192.168.1.1, 00:12:01, FastEtherneto/o 10.0.0.0/24 [90/30720] via 192.168.2.3, 00:12:01, FastEthernet0/1 When a packet is received in R2, the destination IP address is matched against routing table. If R2 receives a packet destined for 10.0.0.1, which route will it choose? There are two routes in the table that seem to match: 10.0.0.0/8 and 10.0.0.0/24. The route with the longest prefix length (also called the most specific route) is the more Chapter 9: Routing and Routers desirable route. Thus, when a packet destined for 10.0.0.1 arrives on R2, it will be forwarded to R3. The important thing to realize about this example is that there may be legitimate addresses within the 10.0.0.0/24 range behind R1 that R2 will never be able to access. Technically, 10.0.0.0/8 is a network, and 10.0.0.0/24 is a subnet. Read on for further clarification. Route Types The routing table can contain six types of routes: Host route A host route is a route to a host. In other words, the route is not to a network. Host routes have a subnet mask of 255.255.255.255, and a prefix length of /32. Subnet A subnet is a portion of a major network. The subnet mask is used to determine the size of the subnet. 10.10.10.0/24 (255.255.255.0) is a subnet. Summary (group of subnets) A summary route is a single route that references a group of subnets. 10.10.0.0/16 (255.255.0.0) would be a summary, provided that subnets with longer masks (such as 10.10.10.0/24) existed. Major network A major network is any classful network, along with its native mask. 10.0.0.0/8 (255.0.0.0) is a major network. Supernet (group of major networks) A supernet is single route that references a group of major networks. 10.0.0.0/7 is a supernet that references 10.0.0.0/8 and 11.0.0.0/8. Default route A default route is shown as 0.0.0.0/0 (0.0.0.0). This route is also called the route of last resort. This is the route that is used when no other route matches the destinatio