多项选择题
A. 6to4 tunneling
B. VPN tunneling
C. GRE tunneling
D. ISATAP tunneling
E. PPP tunneling
F. Teredo tunneling
多项选择题 Which two statements are true regarding EIGRP?（）
多项选择题 As a frame leaves a Layer 3 device, the Layer 2 encapsulation information is changed from what it was when it entered the device. For what two reasons can this happen?（）
多项选择题 For what two purposes does the Ethernet protocol use physical addresses?（）