单项选择题
A.A BGP router can only advertise an EBGP learned route， provided that the route is an IGP route in the routing table.
B.A BGP router can only advertise an IBGP learned route， provided that the route is an IGP route in the routing table.
C.A BGP router can only advertise an IBGP learned route， provided that the route is an IGP route that is not in the routing table.
D.A BGP router can only advertise an EBGP learned route， provided that the route is a metric of 0 in the BGP table.
单项选择题 YouhavearouterrunningBGPfortheMPLSnetworkandOSPFforthelocalLANnetworkatthesalesoffice.ArouteisbeinglearnedfromtheMPLSnetworkthatalsoexistsontheOSPFlocalnetwork.ItisimportantthattherouterchoosesthelocalLANroutebeinglearnedfromthedownstreamswitchrunningOSPFratherthantheupstreamBGPneighbor.Also，ifthelocalOSPFroutegoesaway，theBGProuteneedstobeused.WhatshouldbeconfiguredtomakesurethattherouterwillchoosetheLANnetworkasthepreferredpath？（）
问答题 BGP的Community对于选择最优路径有什么作用？
单项选择题 Refer to the exhibit. R2 and R3 are routers connected using Ethernet services from a service provider and can receive pings from each other. OSPF is configured as the routing protocol but adjacency is not happening. According to the output of the show commands in the exhibit， what could be the most likely cause of the problem？（）