# network 10.10.10.0 With a classful protocol like RIP, you must be careful because, as an example, including the network 10.0.0.0 will include every interface configured with a 10.x.x.x IP address, regardless of subnet mask. RIP does not allow the inclusion of a subnet or inverse mask in the network statements. You can enter a network other than 10.0.0.0, but IOS will convert the entry into the full classful network. The preceding entry results in the following being shown in the configuration: router rip network 10.0.0.0 The configuration that would include all interfaces for Router A as shown in Figure 10-10 would be as follows: router rip version 1 network 10.0.0.0 network 192.168.1.0 network 192.168.2.0 One entry covers both the 10.10.10.0 and 10.20.20.0 networks, but the 192.168 networks each require their own network statements. This is because 192.x.x.x networks are class C networks, while 10.x.x.x networks are class A networks. Chapter 10: Routing Protocols 10.10.10.0/24 192.168.1.0/24 192.168.2.0/24 Router A 10.20.20.0/24 Figure 10-10. Routing protocol network interfaces You won't always want to include every interface that the network statement encom- passes. In the preceding example, we might want to allow RIP on E0/0, but not on E1/1. This can be accomplished with the use of the passive-interface command, which removes an interface from the broader range specified by the network command: router rip version 1 passive-interface Ethernet1/1 network 10.0.0.0 The passive- - interface command causes RIP to ignore updates received on the speci- fied interface. The command also prevents RIP from sending updates on the interface. Routes learned via RIP are identified in the routing table with an R in the first col- umn. This example shows the network 172.16.0.0/16 learned via RIP. The actual network in use is 172.16.100.0/24, but because RIP is classful, the router assumes that the entire 172.16.0.0/16 network is there as well: R3# sho ip route [text removed] Gateway of last resort is 192.168.1.2 to network 0