多项选择题 Enterprise Router R1 connects an Enterprise to the Internet. R1 needs to create and advertise a default route into the Enterprise using EIGRP. The engineer creating the implementation plan has chosen to base this default route on the ip route command, rather than using i p default - network. Which of the following is not a useful step with this style of default route configuration?（）

单项选择题 Router R1 exists in an Enterprise that uses EIGRP as its routing protocol. The show ip route command output on router R1 lists the following phrase: "Gateway of last resort is 1.1.1.1 to network 2.0.0.0". Whic h of the following is most likely to have caused this output to occur on R1?（）

多项选择题 In a lab, R1 connects to R2, which connects to R3. R1 and R2 each have several working interfaces, all assigned addresses in class A network 10.0.0.0. Router R3 has some working interfaces in class A net work 10.0.0.0, and others in class B network 172.16.0.0. The engineer experiments with the auto -summary command on R2 and R3, enabling and disabling the command in various combinations. Which of the following combinations will result in R1 seeing a rout e for 172.16.0.0/16, instead of the individual subnets of class B network 172.16.0.0?（）