单项选择题 Running both IPv4 and IPv6 on a router simultaneously is known as what?（）

单项选择题 What is an appropriate use of a default route?（）

单项选择题 A router has learned three possible routes that could be used to reach a destination network. One route is from EIGRP and has a composite metric of 20514560. Another route is from OSPF with a metric of 782. The last is from RIPv2 and has a metric of 4. Which route or routes will the router install in the routing table?（）