To protect against first-hop router failure， four protocols were developed to ensure IP routing  redundancy. 
Which of the following are they？（）

HSRP is being set up between two Company devices. 
In what three states is it possible for an  HSRP router to be in？（）

R1 and R2 exchange HSRP between each other in the Company network. 
In which three HSRP  states do routers send hello messages？（）

You need to implement a high availability design in the Company routed network. 
Which protocol  allows for the automatic selection and simultaneous use of multiple available gateways as well as  automatic failover between those gateways？（）