Cisco 100-105 - ICND Interconnecting Cisco Networking Devices Part 1 Exam

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Total 711 questions

Which address type does a switch use to make selective forwarding decisions?

  • A. destination IP address
  • B. source MAC address
  • C. source IP address
  • D. source and destination IP address
  • E. destination MAC address E


Answer : Explanation

Explanation:
Switches analyze the destination MAC to make its forwarding decision since it is a layer 2 device.
Routers use the destination IP address to make forwarding decisions.

In which two ways does TCP differ from UDP? (Choose two.)

  • A. TCP provides synchronized communication.
  • B. TCP segments are essentially datagrams.
  • C. TCP provides sequence numbering of packets.
  • D. TCP uses broadcast delivery.
  • E. TCP provides best effort delivery.


Answer : AC

Explanation:
TCP differs from UDP in the following ways: TCP provides best effort delivery.
TCP provides synchronized communication. TCP segments are essentially datagrams.
TCP provides sequence numbering of packets. TCP uses broadcast delivery.

Under which circumstance should a network administrator implement one-way NAT?

  • A. when the network must route UDP traffic
  • B. when traffic that originates outside the network must be routed to internal hosts
  • C. when traffic that originates inside the network must be routed to internal hosts
  • D. when the network has few public IP addresses and many private IP addresses require outside access


Answer : D

Explanation:
NAT operation is typically transparent to both the internal and external hosts. Typically the internal host is aware of the true IP address and TCP or UDP port of the external host. Typically the NAT device may function as the default gateway for the internal host. However the external host is only aware of the public IP address for the NAT device and the particular port being used to communicate on behalf of a specific internal host.

NAT and TCP/UDP -
"Pure NAT", operating on IP alone, may or may not correctly parse protocols that are totally concerned with IP information, such as ICMP, depending on whether the payload is interpreted by a host on the "inside" or "outside" of translation. As soon as the protocol stack is traversed, even with such basic protocols as TCP and UDP, the protocols will break unless NAT takes action beyond the network layer. IP packets have a checksum in each packet header, which provides error detection only for the header. IP datagrams may become fragmented and it is necessary for a NAT to reassemble these fragments to allow correct recalculation of higher-level checksums and correct tracking of which packets belong to which connection. The major transport layer protocols, TCP and UDP, have a checksum that covers all the data they carry, as well as the TCP/UDP header, plus a "pseudo-header" that contains the source and destination IP addresses of the packet carrying the TCP/UDP header. For an originating NAT to pass TCP or UDP successfully, it must recompute the TCP/UDP header checksum based on the translated IP addresses, not the original ones, and put that checksum into the TCP/UDP header of the first packet of the fragmented set of packets. The receiving
NAT must recompute the IP checksum on every packet it passes to the destination host, and also recognize and recompute the TCP/UDP header using the retranslated addresses and pseudo-header. This is not a completely solved problem. One solution is for the receiving NAT to reassemble the entire segment and then recompute a checksum calculated across all packets.
The originating host may perform Maximum transmission unit (MTU) path discovery to determine the packet size that can be transmitted without fragmentation, and then set the don't fragment (DF) bit in the appropriate packet header field. Of course, this is only a one- way solution, because the responding host can send packets of any size, which may be fragmented before reaching the NAT.

Which destination IP address can a host use to send one message to multiple devices across different subnets?

  • A. 172.20.1.0
  • B. 127.0.0.1
  • C. 192.168.0.119
  • D. 239.255.0.1


Answer : D

Explanation:
Multicast is a networking protocol where one host can send a message to a special multicast IP address and one or more network devices can listen for and receive those messages.
Multicast works by taking advantage of the existing IPv4 networking infrastructure, and it does so in something of a weird fashion. As you read, keep in mind that things are a little confusing because multicast was "shoe-horned" in to an existing technology. For the rest of this article, let's use the multicast IP address of
239.255.0.1.

Which option must occur before a workstation can exchange HTTP packets with a web server?

  • A. An ICMP connection must be established between the workstation and the web server.
  • B. A UDP connection must be established between the workstation and its default gateway.
  • C. A TCP connection must be established between the workstation and its default gateway.
  • D. A UDP connection must be established between the workstation and the web server.
  • E. An ICMP connection must be established between the workstation and its default gateway.
  • F. A TCP connection must be established between the workstation and the web server.


Answer : F

Explanation:
HTTP uses TCP port 80.
http://pentestlab.wordpress.com/2012/03/05/common-tcpip-ports/

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Total 711 questions