Cisco 351-001 Online Practice Questions and Exam Preparation

Cisco 351-001 Online Questions & Answers

• Question 581:

  Refer to the exhibit.

  

  Why is the router out of memory?

  A. The router is experiencing a BGP memory leak software defect.
  B. The BGP peers have been up for too long.
  C. The amount of BGP update traffic in the network is too high.
  D. The router has insufficient memory due to the size of the BGP database.
  D. The router has insufficient memory due to the size of the BGP database.

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  Here we can see that this router is running out of memory due to the large size of the BGP routing database. In this case, this router is receiving over 200,000 routes from each of the 4 peers.

• Question 582:

  Which two statements are true about an EPL? (Choose two.)

  A. It is a point-to-point Ethernet connection between a pair of NNIs.
  B. It allows for service multiplexing.
  C. It has a high degree of transparency.
  D. The EPL service is also referred to as E-line.
  C. It has a high degree of transparency.
  D. The EPL service is also referred to as E-line.

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  Ethernet private line (EPL) and Ethernet virtual private line (EVPL) are carrier Ethernet data services defined by the Metro Ethernet Forum. EPL provides a point- to-point Ethernet virtual connection (EVC) between a pair of dedicated

  useretwork interfaces (UNIs), with a high degree of transparency. EVPL provides a point- to-point or point-to-multipoint connection between a pair of UNIs.

  The services are categorized as an E-Line service type, with an expectation of low frame delay, frame delay variation and frame loss ratio. EPL is implemented using a point-to-point (EVC) with no Service Multiplexing at each UNI (physical

  interface), i.e., all service frames at the UNI are mapped to a single EVC (a.k.a. all- to-one bundling).

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

• Question 583:

  Refer to the exhibit,

  

  which type of connection does ERSPAN use to transport traffic from switch 1 to switch 2?

  A. An SVI
  B. A PPTP tunnel
  C. A GRE tunnel
  D. A VLAN
  C. A GRE tunnel

• Question 584:

  DRAG DROP

  Select and Place:

  

  

• Question 585:

  Which option is the origin code when a route is redistributed into BGP?

  A. IGP
  B. EGP
  C. external
  D. incomplete
  E. unknown
  D. incomplete

• Question 586:

  A packet capture log indicates that several router solicitation messages were sent from a local host on the IPv6 segment. What is the expected acknowledgment and its usage?

  A. Router acknowledgment messages will be forwarded upstream, where the DHCP server will allocate addresses to the local host.
  B. Routers on the IPv6 segment will respond with an advertisement that provides an external path from the local subnet, as well as certain data, such as prefix discovery.
  C. Duplicate Address Detection will determine if any other local host is using the same IPv6 address for communication with the IPv6 routers on the segment.
  D. All local host traffic will be redirected to the router with the lowest ICMPv6 signature, which is statically defined by the network administrator.
  B. Routers on the IPv6 segment will respond with an advertisement that provides an external path from the local subnet, as well as certain data, such as prefix discovery.

• Question 587:

  Which statement about OSPF loop prevention is true?

  A. The discard route is generated automatically on the ABR to prevent routing loops.
  B. The ASBR uses type 3 LSAs from non-backbone areas to prevent control-plane routing loops.
  C. The ABR can filter type 3 LSPs to prevent routing loops.
  D. The DN bit ignores LSA types 2, 3, and 5 to prevent routing loops.
  A. The discard route is generated automatically on the ABR to prevent routing loops.

• Question 588:

  Which GET VPN component maintains security policies?

  A. group member
  B. CE
  C. P
  D. key server
  E. PE
  F. GDOI
  D. key server

• Question 589:

  In the DiffServ model, which class represents the highest priority with the lowest drop probability?

  A. AF11
  B. AF13
  C. AF41
  D. AF43
  C. AF41

• Question 590:

  What is a reason for 6PE to use two MPLS labels in the data plane instead of one?

  A. 6PE allows penultimate hop popping and has a requirement that all P routers do not have to be IPv6 aware.
  B. 6PE does not allow penultimate hop popping.
  C. It allows MPLS traffic engineering to work in a 6PE network.
  D. It allows 6PE to work in an MPLS network where 6VPE is also deployed.
  A. 6PE allows penultimate hop popping and has a requirement that all P routers do not have to be IPv6 aware.

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  Q. Why does 6PE use two MPLS labels in the data plane? A. 6PE uses two labels: The top label is the transport label, which is assigned hop-by-hop by the Label Distribution Protocol (LDP) or by MPLS traffic engineering (TE). The bottom label is the label assigned by the Border Gateway Protocol (BGP) and advertised by the internal BGP (iBGP) between the Provider Edge (PE) routers. When the 6PE was released, a main requirement was that none of the MPLS core routers (the P routers) had to be IPv6-aware. That requirement drove the need for two labels in the data plane. There are two reasons why the 6PE needs both labels. PHP Functionality If only the transport label were used, and if penultimate hop popping (PHP) were used, the penultimate hop router (the P router) would need to understand IPv6. With PHP, this penultimate hop router would need to remove the MPLS label and forward the packet as an IPv6 packet. This P router would need to know that the packet is IPv6 because the P router would need to use the correct Layer 2 encapsulation type for IPv6. (The encapsulation type is different for IPv6 and IPv4; for example, for Ethernet, the encapsulation type is 0x86DD for IPv6, while it is 0x0800 for IPv4.) If the penultimate hop router is not IPv6-capable, it would likely put the Layer 2 encapsulation type for IPv4 for the IPv6 packet. The egress PE router would then believe that the packet was IPv4. There is time-to-live (TTL) processing in both the IPv4 and IPv6 headers. In IPv6, the field is called Hop Limit. The IPv4 and IPv6 fields are at different locations in the headers. Also, the Header Checksum in the IPv4 header would also need to be changed; there is no Header Checksum field in IPv6. If the penultimate hop router is not IPv6- capable, it would cause the IPv6 packet to be malformed since the router expects to find the TTL field and Header Checksum field in the header. Because of these differences, the penultimate hop router would need to know it is an IPv6 packet. How would this router know that the packet is an IPv6 packet, since it did not assign a label to the IPv6 Forwarding Equivalence Class (FEC), and there is no encapsulation field in the MPLS header? It could scan for the first nibble after the label stack and determine that the packet is IPv6 if the value is 6. However, that implies that the penultimate hop router needs to be IPv6-capable. This scenario could work if the explicit null label is used (hence no PHP). However, the decision was to require PHP. Load Balancing Typical load balancing on a P router follows this process. The P router goes to the end of the label stack and determines if it is an IPv4 packet by looking at the first nibble after the label stack. If the nibble has a value of 4, the MPLS payload is an IPv4 packet, and the P router load balances by hashing the source and destination IPv4 addresses. If the P router is IPv6-capable and the value of the nibble is 6, the P router load balances by hashing the source and destination IPv6 addresses. If the P router is not IPv6-capable and the value of the nibble is not 4 (it could be 6 if the packet is an IPv6 packet), the P router determines it is not an IPv4 packet and makes the load balancing decision based on the bottom label. In the 6PE scenario, imagine there are two egress PE routers advertising one IPv6 prefix in BGP towards the ingress PE router. This IPv6 prefix would be advertised with two different labels in BGP. Hence, in the data plane, the bottom label would be either of the two labels. This would allow a P router to load balance on the bottom label on a per-flow basis. If 6PE used only the transport label to transport the 6PE packets through the MPLS core, the P routers would not be able to load balance these packets on a per-flow basis unless the P routers were IPv6-capable. If the P routers were IPv6-capable, they could use the source and destination IPv6 addresses in order to make a load balancing decision.

  Reference: http://www.cisco.com/c/en/us/support/docs/multiprotocol-label-switching- mpls/mpls/116061-qa-6pe-00.html