防火墙的技术已经经历了下列哪几个阶段？（） ["包过滤技术","代理技术","硬件技术","状态监视技术"]
（）是一种将贷款本金分段偿还，根据资金的实际占用时间计算利息的还款方式。 ["到期一次还本付息法","等额本息还款法","等额本金还款法","组合还款法"]
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Spanning-Tree Protocol is a link management protocol that provides path redundancy while preventing undesirable loops in the network. For an Ethernet network to function properly， only one active path can exist between two stations. Multiple active paths between stations cause loops in the network. If a loop exists in the network topology， the potential exists for duplication of messages. When loops occur， some switches see stations appear on both sides of the switch. This condition confuses the forwarding algorithm and allows duplicate frames to be forwarded. To provide path redundancy， Spanning-Tree Protocol defines a tree that spans all switches in an extended network. Spanning-Tree Protocol forces certain redundant data paths into a standby （blocked） state. If one network segment in the Spanning-Tree Protocol becomes unreachable， or if Spanning-Tree Protocol costs change， the spanning-tree algorithm reconfigures the spanning-tree topology and reestablishes the link by activating the standby path. Spanning-Tree Protocol operation is transparent to end stations， which are unaware whether they are connected to a single LAN segment or a switched LAN of multiple segments.There is a lab about STP in Cisco CCNP 642-812 / 642- 892 exam. Requirements: You will configure FastEthernet ports 0/12 through 0/24 for users who belong to VLAN 20. Also, all VLAN and VTP configurations are to be completed in global configuration mode as VLAN database mode is being deprecated by Cisco. You are required to accomplish the following tasks: 1. Ensure the switch does not participate in VTP but forwards VTP advertisements received on trunk ports. 2. Ensure all non-trunking interfaces (Fa0/1 to Fa0/24) transition immediately to the forwarding state of Spanning-Tree. 3. Ensure all FastEthernet interfaces are in a permanent non-trunking mode. 4. Place FastEthernet interfaces 0/12 through 0/24 in VLAN 20
“计价规范”中的工程量清单综合单价是一种狭义上的综合单价，在项目单价中不包括（）。 ["A.不能计量的措施项目 ","B.税金 ","C.计日工 ","D.总承包服务费 ","E.规费"]
教师在课堂上要让学生学会自己拿着钥匙去开门。此即（）
