单项选择题
A. simple password
B. HMAC message digest 5
C. Password Authentication Protocol
D. Challenge Handshake Authentication Protocol
单项选择题 Routers A and B are connected with a point-to-point OC-3 interface. Each routers OC-3 interface is configured for both Level 1 and Level 2. The routers are configured in the same area. How many IS-IS adjacencies exist between the two routers?（）
单项选择题 Two Level 1 routers are exchanging Hello packets with different Area IDs.What occurs between these routers?（）
单项选择题 Two Level 2 routers are exchanging Hello packets with different Area IDs.What occurs between these routers?（）