外部不经济，是指一种经济行为对其本身和外部产生出来的负效益。下列选项中，属于外部不经济现象的

A. It supports VLSM.

B. It is used to route between autonomous systems.

C. It confines network instability to one area of the network.

D. It increases routing overhead on the network.

E. It allows extensive control of routing updates.

F. It is simpler to configure than RIP v2.

A. A routed protocol is assigned to an interface and determines the method of packet deliver.

B. A routing protocol determines the path of a packet through a network.

C. A routed protocol determines the path of a packet through a network.

D. A routing protocol operates at the transport layer of the OSI model.

E. A routed protocol updates the routing table of a router.

A. A routing protocol is assigned to an interface and determines the method of packet delivery.

B. A routed protocol is assigned to an interface and determines the method of packet delivery.

C. A routing protocol determines the path of a packet through a network.

D. A routed protocol determines the path of a packet through a network.

E. A routing protocol operates at the transport layer of the OSI model.

F. A routed protocol updates the routing table of a router.

Open Shortes t Path First (OSPF) is a routing protocol developed for Internet Protocol (IP) networks by the Interior Gateway Protocol (IGP) working group of the Internet Engineering Task Force (IETF).Which two statements best describe the OSPF link - state routing pro tocol？（）

A. OSPF sends updates every 10 seconds

B. OSPF sends triggered updates when a network change occurs

C. When a link state is changed, the router that detected the change creates a link - state advertisement (LSA) and propagates it to all OSPF devices using the 224.0.0.6 multicast address

D. OSPF sends summaries of individual link- state entries every 30 minutes to ensure LSDB synchronization

A.RIP is an example of distance vector routing protocols

B.Updates are periodic and include the entire routing table

C.Routing updates are sent only after topology changes

D.The protocol can be useful in hub-and-spoke and hierarchical networks

E.Convergence is usually faster than with link state protocols

F.Each router has its own view of the topology

A. The use of discontiguous subnets is not allowed

B. The use of variable length subnet masks is permitted

C. RIP v1 is a classless routing protocol

D. IGRP supports classless routing within the same autonomous system

E. RIP v2 supports classless routing

A. If using IS-IS as the PE-CE routing protocol, no redistribution is required.

B. If using static routes between the CE and PE routers, no redistribution of other VPN routes is required.

C. If the PE-CE protocol is not BGP, redistribution of other VPN routes from MP-BGP is required.

D. If RIP is the routing protocol that is used between the PE-CE routers, no redistribution is required, but any other protocol will require redistribution.

E. If using OSPF or EIGRP as the PE-CE routing protocol, redistribution is not required, but any other protocol or static route will require redistribution.

A. EIGRP can be used only as the PE-CE routing protocol if the PE and CE routers are in the same AS

B. Other EIGRP AS routes are automatically advertised to the CE router and do not require a redistribution configuration command to be configured

C. Unlike other routing protocols that are used between PE and CE routers, EIGRP supports backdoor links

D. Configure of the VPN is only required on the PE router

g scheme that conserves IP addresses3)multiple vendors4)a network with over 50 routers Which routing protocol fulfills these requirements（）。

A.RIPv1

B.RIPv2

C.EIGRP

D.OSPF

t？As a Network Engineer, it is necessary for you to know how to implement MPLS VPNs between Customer Edge and Provider Edge routers.Refer to the following descriptions, which one is making sense？（）

A. If using OSPF or EIGRP as the PE-CE routing protocol, redistribution is not required, but any other protocol or static route will require redistribution

B. If using IS-IS as the PE-CE routing protocol, no redistribution is required

C. If using static routes between the CE and PE routers, no redistribution of other VPN routes is required

D. If PE-CE protocol is not BGP, redistribution of other VPN routes from MP-BGP is required