简答题

三台路由器，问：在路由器B（即中间的那台路由器）上的E0/1的IN方向做一个ACL，要求路由器A可以TELNET路由器C，但是路由器C不可以TELNET路由器A。要求写出ACL命令行。

单项选择题Whiletroubleshootinganetwork，youneedtoverifythelivenessofhostsinthesubnet192.168.1.64 26.Allofthehostsareabletoreplytopingrequests.Howwouldyouconfirmtheexistingnodesusingonesinglecommand？（）

A.ping 192.168.1.255
B.ping with sweep option
C.ping 192.168.1.127
D.ping 192.168.1.64
E.ping with broadcast option

单项选择题Whichmechanismcanyouusetoachievesub-secondfailoverforlinkfailuredetectionwhenaswitchedEthernetmediaisusedandlossofsignalisnotsupportedbythelinkprovider？（）

A.OSPF standard hellos
B.Cisco Discovery Protocol link detection
C.Bidirectional Forwarding Detection
D.Fast Link Pulse
E.autonegotiation

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?（）

A.Ethernet interfaces were configured as point-to-point.
B.Process IDs are not matching.
C.Configured bandwidths do not match on both interfaces.
D.Broadcasts and multicast are not being propagated over the Ethernet services.
E.OSPF cost does not match on both interfaces.

问答题itisbelongafamilyofiproutingprotocols，eachrouterhaveapartialmapofnetwork，whatistheroutingprotocol？

问答题什么环境下需要用组播？