多项选择题 You have been asked to establish reachability between Router 1s and Router 2s loopback addresses as shown in the exhibit.Which two steps will accomplish this task?（）

单项选择题 What is the purpose of a network mask?（）

单项选择题 Given the configuration and routing table shown in die exhibit,which routes will be advertised to OSPF neighbors because of the demo policy?（）