Cisco 200-125 Online Practice Questions and Exam Preparation

Cisco 200-125 Online Questions & Answers

• Question 311:

  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
  B. when traffic that originates outside the network must be routed to internal hosts

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  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.

• Question 312:

  Which type of access list compares source and destination IP addresses?

  A. extended
  B. standard
  C. IP named
  D. reflexive
  A. extended

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  Extended ACLs compare the source and destination addresses of the IP packets to the addresses configured in the ACL in order to control traffic. You can also make extended ACLs more granular and configured to filter traffic by criteria such as: Protocol Port numbers Differentiated services code point (DSCP) value Precedence value State of the synchronize sequence number (SYN) bit

• Question 313:

  Which MTU size can cause a baby giant error?

  A. 1500
  B. 9216
  C. 1600
  D. 1518
  C. 1600

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  Explanation: http://www.cisco.com/c/en/us/support/docs/switches/catalyst-4000-series-switches/29805-175.html

• Question 314:

  Which two actions must you take to correctly configure PPPoE on a client? (Choose two )

  A. Define a dialer interface
  B. Create a dialer pool and bind it to the virtual template
  C. Define a virtual template interface
  D. Create a dialer pool and bind it to the physical interface.
  E. Create a BBA group and link it to the dialer interface
  A. Define a dialer interface
  D. Create a dialer pool and bind it to the physical interface.

• Question 315:

  Which VLAN bridge priority value is assigned by the set spantree root command?

  A. 8192
  B. 16384
  C. 28672
  D. 32768
  A. 8192

• Question 316:

  Which three encapsulation layers in the OSI model are combined into the TCP/IP application layer?(choose three)

  A. transport
  B. application
  C. session
  D. presentation
  E. data link
  F. network
  B. application
  C. session
  D. presentation

• Question 317:

  In which circumstance are multiple copies of the same unicast frame likely to be transmitted in a switched LAN?

  A. during high traffic periods
  B. after broken links are re-established
  C. when upper-layer protocols require high reliability
  D. in an improperly implemented redundant topology
  E. when a dual ring topology is in use
  D. in an improperly implemented redundant topology

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  If we connect two switches via 2 or more links and do not enable STP on these switches then a loop (which creates multiple copies of the same unicast frame) will occur. It is an example of an improperly implemented redundant topology.

• Question 318:

  Which configuration enables OSPF for network 192.168.1.0/24?

  A. router ospfrouter-id 192.168.1.0
  B. router ospf 1network 192.168.1.0 255.255.255.0 area 0
  C. router ospf 1neighbor 192.168.1.0
  D. router ospf 1area 0 virtual-link 192.168.1.0
  B. router ospf 1network 192.168.1.0 255.255.255.0 area 0

• Question 319:

  Drag and Drop

  Select and Place:

  

  

• Question 320:

  what is the minimum Ethernet frame size?

  A. 32bytes
  B. 64bytes
  C. 1024bytes
  D. 1500bytes
  B. 64bytes