思科认证考试

Assuming that an IP packet is sent from a source address in VLAN1 to a destination address in VLAN2 through a layer-3 switch, which part of the packet will be changed?（）A、Layer 2 TTLB、Layer 3 TTLC、Layer 3 source addressD、Layer 3 destination address

题目

Assuming that an IP packet is sent from a source address in VLAN1 to a destination address in VLAN2 through a layer-3 switch, which part of the packet will be changed?（）

  • A、Layer 2 TTL
  • B、Layer 3 TTL
  • C、Layer 3 source address
  • D、Layer 3 destination address
如果没有搜索结果，请直接 联系老师 获取答案。
如果没有搜索结果，请直接 联系老师 获取答案。
相似问题和答案

第1题：

Anytime a host or a router has an IP datagram to send to another host or router, it has the（　）address of the receiver. This address is obtained from the DNS if the sender is the host or it is found in a routing table if the sender is a router. But the IP data gram must be（　） in a frame to be able to pass through the physical network. This means that the sender needs the （　）address of the receiver. The host or the router sends an ARP query packet. The packet includes the physical and IP addresses of the sender and the IP address of the receiver. Because the sender does not know the physical address of the receiver, the query is（　） over the network.Every host or router on the network receives and processes the ARP query packet, but only the intended recipient recognizes its IP address and sends back an ARP response packet.The response packet contains the recipient's IP and physical addresses. The packet is（请作答此空） directly to the inquirer by using the physical address received in the query packet.

A. multicast
B. unicast
C. broadcast
D. multiple unicast

答案：B
解析：
任何时候主机或路由器要发送 IP 数据报发送给另一主机或路由器时，都需要知道接收方的逻辑地址。发送主机从 DNS 获得该地址，发送路由器则在路由表中找到该地址。但 IP 数据报必须封装在帧中才能通过物理网络。这意味着发送者需要知道接收者的物理地址。主机或路由器需发送 ARP 查询报文，该报文分组包含发送者的物理地址和 IP 地址及接收者的 IP 地址。这是因为送者不知道接收者的物理地址，所以需在全网广播报文。网络上的每个主机或路由器都能接收并处理该 ARP 查询报文，但只有预期的接收者识别其 IP 地址并响应该 ARP 报文。响应报文包含接收者的 IP 地址和物理地址。包含了接收者物理地址的响应报文分组通过单播的方式直接发送给发送者。

第2题：

PTN： Packet Transport Network（分组传送网络） ，其中Packet（分组）是指具备（）、多业务（IP化业务）接入、业务带宽共享和分类QOS保障管理能力。 

  • A、IP化分组内核
  • B、大颗粒交换内核
  • C、光信号交换内核

正确答案:A

第3题：

阅读下面的短文，回答问题 [When an IP packet arrives at a router, generally the router looks at the destination address of the packet, and forwards the packet to one of its network interfaces. The forwarding decision is usually done by looking up the destination address from another data structure called a forwarding table. The forwarding table is created by the router using the routing table and possible routing policies existing in the router. The router then creates a table where it lists which networks are accessible through which of the router’s network interfaces. An IP router looks at every IP packet individually and does the forwarding decision on a packet-by-packet basis. If something changes in the router’s routing table, a packet can take a different route from a preceding packet even if it has the same destination.] From the paragraph above，we can see that the router （ ） a forwarding table according to the routing table and possible routing policies existing in the router. When an IP packet arrives at a router, the （ ） part of packet is normally checked by the router. An IP router checks every IP Packet individually and makes the forwarding decision based on （ ）.

A．is generating B．generate C．is generated D．generates A．forwarding table B．network interfaces C．routing policies D．destination address A．the destination address and network interfaces B．forwarding table and network interfaces C．the destination address and forward table D．routing policies and routing table


正确答案：D,D,C

第4题：

给了两段documentation里的描述，问这个时候发哪种类型的ICMP包。 The interface on which the packet comes into the router is the same interface on which the packet gets routed out. The subnet or network of the source IP address is on the same subnet or network of the next-hop IP address of the routed packet.


正确答案:ICMP类型5重定向消息。

第5题：

A router receives a packet from a neighbor with an MPLS shim header value of 0.What does the router do with this packet?（）

  • A、It performs a label pop operation and an IP lookup.
  • B、It performs a label swap operation and an IP lookup.
  • C、It sends an error message toward the egress router.
  • D、It sends an error message toward the ingress router.

正确答案:A

第6题：

Traditional IP packet forwarding analyzes the（ ）IP address contained in the network layer header of each packet as the packet travels from its source to its final destination.A router analyzes the destination IP address independently at each hop in the network.Dynamic（ ）protocols or static configuration builds the database needed to analyze the destination IP address（the routing table）.The process of implementing traditional IP routing also is called hop-by-hop destination-based（ ）routing.Although successful，and obviously widely deployed，certain restrictions，which have been realized for some time，exist for this method of packet forwarding that diminish is（请作答此空）.New techniques are therefore required to address and expand the functionality of an IP-based network infrastructure.This first chapter concentrates on identifying these restrictions and presents a new archiecture，known as multiprotocol（ ）switching，that provides solutions some of these restrictions.

A.reliability
B.flexibility
C.stability
D.capability

答案：B
解析：
传统的IP数据包转发分析目的IP地址,该地址包含在每个从源到最终目的地的网络层数据包的头部。一个路由器的分析目的IP地址，该地址独立在网络中的每跳。动态路由协议或静态配置构建数据库，该数据数据库需要分析目的IP地址（路由表）。实施传统的IP路由的过程也叫作基于目的地的逐条单播路由。虽然成功而且明显得广泛部署,并实现了一段时间，但是必然有某些限制,这种数据包转发方法的存在是减少了灵活性。新技术是因此需要地址和扩展一个基于ip的网络基础设施的功能。第一章集中在识别一种新的架构的限制条件和反馈,该架构众所周知是多协议标签交换,它为其中的一些限制条件提供解决方案。

第7题：

What field in IP packet is used for classification by QOS？


正确答案:TOS byte.

第8题：

A router receives a packet from a neighbor with an MPLS shim header value of 0.What does the router do with this packet?()

A. It performs a label pop operation and an IP lookup.

B. It performs a label swap operation and an IP lookup.

C. It sends an error message toward the egress router.

D. It sends an error message toward the ingress router.


参考答案：A

第9题：

Which statement correctly describes the disabling of IP TTL propagation in an MPLS network？（）

  • A、The TTL field from the IP packet is copied into the TTL field of the MPLS label header at the ingress edge LSR
  • B、TTL propagation cannot be disabled in an MPLS domain
  • C、TTL propagation is only disabled on the ingress edge LSR
  • D、The TTL field of the MPLS label header is set to 255
  • E、The TTL field of the IP packet is set to 0

正确答案:D

第10题：

If the router R1 has a packet with a destination address 192.168.1.255, what describes the operation of the network（）。

  • A、R1 will forward the packet out all interfaces.
  • B、R1 will drop this packet because this it is not a valid IP address.
  • C、As R1 forwards the frame containing this packet, Sw-A will add 192.168.1.255 to its MAC table.
  • D、R1 will encapsulate the packet in a frame with a destination MAC address of FF-FF-FF-FF-FF-FF
  • E、As R1 forwards the frame containing this packet, Sw-A will forward it to the device assigned the IP address of 192.168.1.255.

正确答案:B

更多相关问题
相关内容