Cisco 642-902 Online Practice Questions and Exam Preparation

Cisco 642-902 Online Questions & Answers

• Question 171:

  Refer to the graphic.

  

  What optional EIGRP configurations will be required in order to achieve full connectivity within AS 100?

  A. Use the EIGRP no auto-summary command on R1 and R2.
  B. Use the EIGRP no auto-summary command on R3 and R4.
  C. Use the passive interface on the R1 and R2 interface that connects to the 10.1.1.0/24 and 10.1.2.0/24 subnet respectively.
  D. Use the passive interface command between the R3 and R1 connection and between the R3 and R2 connection.
  E. Use the variance command on R3.
  A. Use the EIGRP no auto-summary command on R1 and R2.

  ---

  EIGRP automatically summarizes routes at the classful boundary, the boundary where the network address ends as defined by class-based addressing. In most cases, auto summarization is a good thing, keeping the routing tables as compact as possible In the presence of discontiguous subnetworks, automatic summarization must be disabled for routing to work properly. To turn off auto-summarization, use the following command: Router(config-router)#no auto-summary

• Question 172:

  You are troubleshooting an OSPF problem where external routes are not showing up in the OSPF database. Which two options are valid checks that should be performed first to verify proper OSPF operation? (Choose two.)

  A. Are the ASBRs trying to redistribute the external routes into a totally stubby area?
  B. Are the ABRs configured with stubby areas?
  C. Is the subnets keyword being used with the redistribution command?
  D. Is backbone area (area 0) contiguous?
  E. Is the CPU utilization of the routers high?
  A. Are the ASBRs trying to redistribute the external routes into a totally stubby area?
  C. Is the subnets keyword being used with the redistribution command?

  ---

  A totally stubby stubby area cannot have an ASBR so it will discard this type of LSA (LSA Type 5) -> A is a valid check.

  Each stubby area needs an ABR to communicate with other areas so it is normal -> B is not a valid check.

  When pulling routes into OSPF, we need to use the keyword "subnets" so that subnets will be redistributed too. For example, if we redistribute these EIGRP routes into OSPF:

  +

  10.0.0.0/8

  +

  10.10.0.0/16

  +

  10.10.1.0/24

  without the keyword "subnets"

  router ospf 1 redistribute eigrp 1

  Then only 10.0.0.0/8 network will be redistributed because other routes are not classful routes, they are subnets. To redistribute subnets we must use the keyword "subnets"

  router ospf 1

  redistribute eigrp 1 subnets

  -> C is a valid check.

  We don't need to care if area 0 is contiguous or not -> D is not a valid check. CPU utilization cannot be the cause for this problem -> E is not a valid check.

• Question 173:

  Which three are characteristics of IPv6? (Choose three.)

  A. An IPv6 address is 128 bits long.
  B. An IPv6 header is 20 bits long.
  C. An IPv6 header contains the next header field.
  D. An IPv6 header contains the protocol field.
  E. IPv6 routers send RA messages.
  F. An IPv6 header contains the header checksum field.
  A. An IPv6 address is 128 bits long.
  C. An IPv6 header contains the next header field.
  E. IPv6 routers send RA messages.

  ---

  All IPv6 addresses are 128 bits long to accommodate a far larger number of stations than what was possible with the 32 bit IPv4 addresses.

  The following displays the IPv6 header field in detail:

  IPv6 header:

  

  Version. 4 bits.

  IPv6 version number.

  Traffic Class. 8 bits.

  Internet traffic priority delivery value.

  Flow Label. 20 bits.

  Used for specifying special router handling from source to destination(s) for a sequence of packets.

  Payload Length. 16 bits unsigned.

  Specifies the length of the data in the packet. When cleared to zero, the option is a hop-by- hop Jumbo payload.

  Next Header. 8 bits.

  Specifies the next encapsulated protocol. The values are compatible with those specified for the IPv4 protocol field.

  Hop Limit. 8 bits unsigned.

  For each router that forwards the packet, the hop limit is decremented by 1. When the hop limit field reaches zero, the packet is discarded. This replaces the TTL field in the IPv4 header that was originally intended to be used as a time based

  hop limit.

  Source address. 16 bytes.

  The IPv6 address of the sending node.

  Destination address. 16 bytes.

  The IPv6 address of the destination node.

  Reference: http://www.networksorcery.com/enp/protocol/ipv6.htm

• Question 174:

  Refer to the exhibit.

  

  OSPF is running throughout the network and RIP is being redistributed into OSPF in R2. You want to minimize the propagation of LSAs into and out of Area 1. Which OSPF feature would be best to achieve this goal?

  A. stub
  B. totally stubby
  C. NSSA
  D. totally NSSA
  D. totally NSSA

  ---

  We need to redistribute RIP from R1 to Area 1 so Area 3 cannot be a stub or totally stubby area. To minimize the propagation of LSAs into and out of Area 1 we should configure it as a totally NSSA. Notice that a NSSA allows LSA Type 3 and 7

  while a Totally NSSA only allows LSA Type 7

  Note:

  Both Totally Stubby Area and Totally Stubby NSSA do not accept external AS routes or inter- area routes (LSA Types 3, 4 and 5). They recognize only intra-area routes and the default route 0.0.0.0. The main difference between them is Totally

  Stubby NSSA accepts routes from other AS while Totally Stubby Area does not.

  Below summarizes the LSA Types allowed and not allowed in area types:

  Area Type Type 1 and 2 Type 3 (from Type Type Type

  (within area) other areas) 4 5 7

  Standard and Yes Yes Yes Yes No

  backbone

  Stub Yes Yes No No No

  Totally stubby Yes No No No No

  NSSA Yes Yes No No Yes

  Totally (stubby) Yes No No No Yes

  NSSA

• Question 175:

  Refer to the exhibit.

  

  Which statement is true about the configuration?

  A. RTA will not establish an OSPF adjacency with RTB.
  B. RTA will not accept OSPF hello packets from RTB.
  C. RTA will send OSPF hello packets, but will not send OSPF updates.
  D. RTA will send OSPF updates, but will not establish an adjacency with RTB.
  A. RTA will not establish an OSPF adjacency with RTB.

  ---

  Passive-interface command is used to disable sending updates out from a specific interface. For OSPF it prevents Hello packets from being sent out or received through the interface. This will not allow to create a neighbor adjacency and

  prevent a router from learning prefixes from those neighbors.

  For RIP, configuring an interface as passive will still allow the interface to listen to incoming routing updates for other RIP neighbors, but the interface will no longer send them.

  Note: The passive-interface command is used in router configuration mode, not interface mode.

• Question 176:

  To create an NSSA totally stubby area in Area 1, what commands should be configured on the NSSA ABR?

  A. router ospf 1 area 1 nssa
  B. router ospf 1 area 1 nssa no-summary
  C. router ospf 1 area 1 nssa no-redistribution
  D. router ospf 1 area 1 nssa default-information originate
  E. router ospf 1 area 1 nssa default-information originate metric-type 2
  B. router ospf 1 area 1 nssa no-summary

  ---

  Reference:

  http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a88.shtml (See the topic: defining an NSSA totally stub area)

• Question 177:

  What number is a valid representation for the 200F:0000:AB00:0000:0000:0000:0000/56 IPv6 prefix?

  A. 200F:0:0:AB/56
  B. 200F:0:AB00::/56
  C. 200F::AB00/56
  D. 200F:AB/56
  B. 200F:0:AB00::/56

  ---

  The 0s are truncated.

• Question 178:

  Refer to the Exhibit.

  

  What is the correct configuration to enable router P4 to exchange RIP routing updates with router P1 but not with router P3?

  A. P4(Config)# interface fa0/0 P4(Config-if)# neighbor 192.168.10.3 P4(config-if)# passive-interface fa0/0
  B. P4(config)# router rip P4(config-router)#neighbor 192.168.10.3 P4(Config-router)#passive-interface fa0/0
  C. P4(config)# interface fa0/0 P4(config-if)# neighbor 192.168.10.3 P4(config-if)# passive interface192.168.10.34
  D. P4(config)# router rip P4(config-router)# neighbor 162.168.10.34 no broadcast P4(config-router)# passive-interface fa0/0
  B. P4(config)# router rip P4(config-router)#neighbor 192.168.10.3 P4(Config-router)#passive-interface fa0/0

  ---

  When you configure router P1 to be the nieghtobr of P4 with a passive interface, the RIP routing updates will be exchanged with the neighbor only.

• Question 179:

  Which BGP option is required when load sharing over multiple equal-bandwidth parallel links from a single CE router to a single ISP router over eBGP?

  A. eBGP Multipath
  B. eBGP Multihop
  C. BGP Synchronization
  D. Public AS numbers
  B. eBGP Multihop

  ---

  The eBGP multihop allows a neighbor connection between two external peers that do not have direct connection. The multihop is only for eBGP and not for iBGP. For example, in the topology below router A wants to establish neighbor relationship with the loopback0 of router B (to allow load balancing), which does not have direct connection so it must use "ebgp-multihop"

  

  For your reference, the full configurations of both router A and B are shown below:

  

  Note: If router B wants to establish neighbor relationship with the directly connected interface of router A, it only needs these commands:

  

  But notice the traffic from router B would be sent to 172.16.10.2 interface only and load balancing would not take place.

  (Reference: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c95bb.shtml)

• Question 180:

  Router R1, a branch router, connects to the Internet using DSL. Some traffic flows through a GRE and IPsec tunnel, over the DSL connection, destined for an Enterprise network. Which of the following answers best describes the router's logic that tells the router, for a given packet, to apply GRE encapsulation to the packet?

  A. When the packet received on the LAN interface is permitted by the ACL listed on the tunnel gre acl command under the incoming interface
  B. When routing the packet, matching a route whose outgoing interface is the GRE tunnel interface
  C. When routing the packet, matching a route whose outgoing interface is the IPsec tunnel interface
  D. When permitted by an ACL that was referenced in the associated crypto map
  B. When routing the packet, matching a route whose outgoing interface is the GRE tunnel interface

  ---

  As for the correct answer, the process of routing a packet out a GRE tunnel interface triggers the GRE encapsulation action. As for the incorrect answers: There is no tunnel gre acl command. There is no IPsec tunnel interface. Finally, one answer refers to logic that would describe a router's logic when determining whether to encapsulate a packet into an IPsec tunnel.