31 Days Before Your CCNA Exam

Day 14 193The remote networks that R1 does not know about are as follows:■■■172.16.1.0/24: The LAN on R2192.168.1.0/24: The serial network between R2 and R3192.168.2.0/24: The LAN on R3Static Routes Using the “Next Hop” ParameterUsing the “next hop” parameter, R1 can be configured with three static routes—one for each of thenetworks R1 does not yet know about. Example 14-2 shows the command syntax.Example 14-2Static Route Configuration with “Next Hop” ParameterR1(config)#ip route 172.16.1.0 255.255.255.0 172.16.2.2R1(config)#ip route 192.168.1.0 255.255.255.0 172.16.2.2R1(config)#ip route 192.168.2.0 255.255.255.0 172.16.2.2The interface that routes to the next hop must be “up” and “up” before the static routes can beentered in the routing table. Example 14-3 verifies that the static routes are now in the routingtable.Example 14-3R1 Routing Table After Static Routes Are ConfiguredR1#show ip routeGateway of last resort is not set172.16.0.0/24 is subnetted, 3 subnetsS 172.16.1.0 [1/0] via 172.16.2.2C 172.16.2.0 is directly connected, Serial0/0/0C 172.16.3.0 is directly connected, FastEthernet0/0S 192.168.1.0/24 [1/0] via 172.16.2.2S 192.168.2.0/24 [1/0] via 172.16.2.2R1#Notice that a route exists to the 172.16.2.0/24 network, which the “next hop” 172.16.2.2 belongsto. After performing a recursive lookup to find the exit interface, R1 will send packets for each ofthe three static routes out the Serial 0/0/0 interface.Static Routes Using the Exit Interface ParameterTo avoid a recursive lookup and have a router immediately send packets to the exit interface, configurethe static route using the exit-interface parameter instead of the “next hop” (ip-address)parameter.For example, on R2 we can configure a static route to the 172.16.3.0/24 network and specify theSerial 0/0/0 interface as the exit interface:R2(config)#ip route 172.16.3.0 255.255.255.0 serial 0/0/0