单项选择题
A. physical layer issues
B. no spanning tree loops
C. use of non-default HSRP timers
D. failure to set the command standby 35 preempt
单项选择题 Exhibit Which command will ensure that Company2 will be the primary router for traffic using the gateway address of 172.16.15.20？ （）
单项选择题 Refer to the exhibit. What statement is true based upon the configuration of router R1 and router R2？（）
单项选择题 .Refer to the exhibit and the partial configuration on routers R1 and R2. Hot Standby Routing Protocol （HSRP） is configured on the network to provide network redundancy for the IP traffic. The network administrator noticed that R2 does not become active when the R1 serial0 interface goes down. What should be changed in the configuration to fix the problem？ （）