Cisco 351-001 Online Practice Questions and Exam Preparation

Cisco 351-001 Online Questions & Answers

• Question 771:

  Which two statements about OSPF default route injection are true? (Choose two.)

  A. The ABR requires manual configuration to send a default route into an NSSA area.
  B. The ABR injects a default route into a Totally Stub Area.
  C. In a stub area, the ASBR generates a summary LSA with link-state ID 0.0.0.0.
  D. If the default route is missing from the routing table, the ASBR can use the default- information originate command to advertise the default into the OSPF domain.
  E. By default, OSPF normal areas will generate default routes into the routing domain if a default route exists.
  A. The ABR requires manual configuration to send a default route into an NSSA area.
  B. The ABR injects a default route into a Totally Stub Area.

• Question 772:

  Refer to the exhibit.

  

  If you change the Spanning Tree Protocol from pvst to rapid-pvst, what is the effect on the interface Fa0/1 port state?

  A. It transitions to the listening state, and then the forwarding state.
  B. It transitions to the learning state and then the forwarding state.
  C. It transitions to the blocking state, then the learning state, and then the forwarding state.
  D. It transitions to the blocking state and then the forwarding state.
  C. It transitions to the blocking state, then the learning state, and then the forwarding state.

  ---

  First, the port will transition to the blocking state, immediately upon the change, then it will transition to the new RSTP states of learning and forwarding.

  Port States

  There are only three port states left in RSTP that correspond to the three possible operational states. The 802.1D disabled, blocking, and listening states are merged into a unique 802.1w discarding state.

  STP (802.1D) Port State

  RSTP (802.1w) Port State

  Is Port Included in Active Topology?

  Is Port Learning MAC Addresses?

  Disabled

  Discarding

  No

  No

  Blocking

  Discarding

  No

  No

  Listening

  Discarding

  Yes

  No

  Learning

  Learning

  Yes

  Yes

  Forwarding

  Forwarding

  Yes

  Yes

• Question 773:

  Which IPv6 tunneling type establishes a permanent link between IPv6 domains over IPv4?

  A. IPv4-compatible tunneling
  B. ISATAP tunneling
  C. 6to4 tunneling
  D. manual tunneling
  D. manual tunneling

  ---

  A manually configured tunnel is equivalent to a permanent link between two IPv6 domains over an IPv4 backbone. The primary use is for stable connections that require regular secure communication between two edge routers or between an end system and an edge router, or for connection to remote IPv6 networks.

  Reference:

  http://www.cisco.com/c/en/us/td/docs/ios/ipv6/configuration/guide/12_4t/ipv6_12_4t_book/i p6-tunnel.html

• Question 774:

  What are two advantages to using Asynchronous mode instead of Demand mode for BFD? (Choose two.)

  A. Asynchronous mode requires half as many packets as Demand mode for failure detection.
  B. Asynchronous mode can be used in place of the echo function.
  C. Asynchronous mode supports a larger number of BFD sessions.
  D. Asynchronous mode requires one fourth as many packets as Demand mode for failure detection.
  E. Asynchronous mode's round-trip jitter is less than that of Demand mode.
  A. Asynchronous mode requires half as many packets as Demand mode for failure detection.
  B. Asynchronous mode can be used in place of the echo function.

  ---

  Pure Asynchronous mode is advantageous in that it requires half as many packets to achieve a particular Detection Time as does the Echo function. It is also used when the Echo function cannot be supported for some reason. Reference: https://tools.ietf.org/html/rfc5880

• Question 775:

  Refer to the exhibit.

  

  Service provider SP 1 is running the MPLS-VPN service. The MPLS core network has MP- BGP configured with RR-1 as route reflector. What will be the effect on traffic between PE1 and PE2 if router P1 goes down?

  A. No effect, because all traffic between PE1 and PE2 will be rerouted through P2.
  B. No effect, because P1 was not the only P router in the forwarding path of traffic.
  C. No effect, because RR-1 will find an alternative path for MP-BGP sessions to PE-1 and PE-2.
  D. All traffic will be lost because RR-1 will lose the MP-BGP sessions to PE-1 and PE-2.
  D. All traffic will be lost because RR-1 will lose the MP-BGP sessions to PE-1 and PE-2.

  ---

  If the connection to the route reflector goes down, then routes from PE-1 will not get advertised to PE2, and vice versa. Route reflectors are critical in an MPLS VPN such as the one shown, which is why it is a best practice to have multiple route reflectors in this kind of network.

• Question 776:

  Which two statements about Layer 2 Frame Prioritization bits are true? (Choose two.)

  A. 802.1Q frame headers carry the CoS value in the three most-significant bits of the 2- byte Tag Control Information field.
  B. ISL frame headers carry an IEEE 802.1P CoS value in the three least-significant bits of the 2-byte User field.
  C. ISL frame headers carry an IEEE 802.1P CoS value in the three most-significant bits of the 1-byte User field.
  D. On 802.1Q trunks, traffic in the native VLAN is carried in 802.1Q frames.
  E. Only 802.1Q and ISL frame types can carry CoS information.
  F. On 802.1Q trunks, traffic in the native VLAN is carried in 802.1P frames.
  A. 802.1Q frame headers carry the CoS value in the three most-significant bits of the 2- byte Tag Control Information field.
  E. Only 802.1Q and ISL frame types can carry CoS information.

• Question 777:

  What is Nagle's algorithm used for?

  A. To increase the latency
  B. To calculate the best path in distance vector routing protocols
  C. To calculate the best path in link state routing protocols
  D. To resolve issues caused by poorly implemented TCP flow control.
  D. To resolve issues caused by poorly implemented TCP flow control.

  ---

  Silly window syndrome is a problem in computer networking caused by poorly implemented TCP flow control. A serious problem can arise in the sliding window operation when the sending application program creates data slowly, the receiving application program consumes data slowly, or both. If a server with this problem is unable to process all incoming data, it requests that its clients reduce the amount of data they send at a time (the window setting on a TCP packet). If the server continues to be unable to process all incoming data, the window becomes smaller and smaller, sometimes to the point that the data transmitted is smaller than the packet header, making data transmission extremely inefficient. The name of this problem is due to the window size shrinking to a "silly" value. When there is no synchronization between the sender and receiver regarding capacity of the flow of data or the size of the packet, the window syndrome problem is created. When the silly window syndrome is created by the sender, Nagle's algorithm is used. Nagle's solution requires that the sender sends the first segment even if it is a small one, then that it waits until an ACK is received or a maximum sized segment (MSS) is accumulated.

  Reference: http://en.wikipedia.org/wiki/Silly_window_syndrome

• Question 778:

  Which two statements about IPv4 and IPv6 networks are true? (Choose two.)

  A. In IPv6, hosts perform fragmentation.
  B. IPv6 uses a UDP checksum to verify packet integrity.
  C. In IPv6, routers perform fragmentation.
  D. In IPv4, fragmentation is performed by the source of the packet.
  E. IPv4 uses an optional checksum at the transport layer.
  F. IPv6 uses a required checksum at the network layer.
  A. In IPv6, hosts perform fragmentation.
  B. IPv6 uses a UDP checksum to verify packet integrity.

• Question 779:

  Which BGP aggregate address configuration advertises only the aggregate address, with attributes inherited from the more specific routes?

  A. summary-only as-set
  B. as-set
  C. summary
  D. summary-only
  A. summary-only as-set

  ---

  Example: router bgp 300 neighbor 2.2.2.2 remote-as 100 neighbor 3.3.3.3 remote-as 200 neighbor 4.4.4.4 remote-as 400 aggregate-address 160.0.0.0 255.0.0.0 summary-only as-set

  !--- With the as-set configuration command, the aggregate !--- inherits the attributes of the more-specific routes. Reference: http://www.cisco.com/c/en/us/support/ docs/ip/border-gateway-protocol- bgp/5441-aggregation.html

• Question 780:

  Which three statements about the route preference of IS-IS are true? (Choose three.)

  A. An L1 path is preferred over an L2 path.
  B. An L2 path is preferred over an L1 path.
  C. Within each level, a path that supports optional metrics is preferred over a path that supports only the default metric.
  D. Within each level of metric support, the path with the lowest metric is preferred.
  E. The Cisco IS-IS implementation usually performs equal cost path load balancing on up to eight paths.
  F. Both L1 and L2 routes will be installed in the routing table at the same time.
  A. An L1 path is preferred over an L2 path.
  C. Within each level, a path that supports optional metrics is preferred over a path that supports only the default metric.
  D. Within each level of metric support, the path with the lowest metric is preferred.

  ---

  Given multiple possible routes to a particular destination, an L1 path is preferred over an L2 path. Within each level, a path that supports the optional metrics is preferred over a path that supports only the default metric. (Again, Cisco supports only the default metric, so the second order of preference is not relevant to Cisco routers.) Within each level of metric support, the path with the lowest metric is preferred. If multiple equal-cost, equal-level paths are found by the Decision process, they are all entered into the route table. The Cisco IS-IS implementation usually performs equal-cost load balancing on up to six paths.

  Reference: http://www.realccielab.org/operation-of-integrated-is-is.html