Which three characteristics apply to IS - IS but not to OSPF?（） uses a default IOS metric of 10 on each interface。 uses an on - demand circuit to reduce the hello and LSA flooding across switched WAN li nks,such as ISDN。 uses a DIS and a backup DIS to present the psuedo - node on the LAN。 encapsulates PDUs directly into a data - link frame。 uses stubby areas to improve network scalability。 runs PRC (Partial Route Calculations) to calculate IP re achability informatio。
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。
社会组织协调与公众关系的方式是（）。 人际传播。 组织传播。 大众传播。 自身传播。
集料的相对密度.吸水率对沥青混合料的力学性能的影响是明显的，因此吸水率为（）的石料比较合适。 0.5%～1%。 2%～3%。 0.3%～0.7%。 1%～1.5%。
下列4种运输中，等量换算周转量占有的资源最少的是（）。
