Cisco 642-902 Online Practice Questions and Exam Preparation

Cisco 642-902 Online Questions & Answers

• Question 1:

  What technique should be used on BGP edge routers to prevent a multi-homed autonomous system from becoming a transit system?

  A. Advertise with a high MED value all networks that are discovered via external BGP.
  B. Set the no-export community attribute on all networks that are advertised externally.
  C. Remove the AS-Path information on all routes in the BGP table prior to advertising externally.
  D. Set the origin code to incomplete for all networks that are discovered via external BGP.
  E. Only advertise networks externally if they have been discovered via internal BGP.
  F. Use an outgoing distribution list to filter all networks not originating from inside the autonomous system.
  F. Use an outgoing distribution list to filter all networks not originating from inside the autonomous system.

  ---

  The minimum configuration that guarantees you won't become a transit AS is shown in the following example: router bgp 65000 neighbor 10.1.1.1 filter-list 1 out ! ip as-path access-list 1 permit ^$ In this example, the outgoing filter list says that all traffic not sourced from the local AS, should not be advertised. This will prevent the announcement of routes that originated from other Autonomous Systems, and prevent traffic destined for networks in another AS from going through your AS. This is useful real-world information to know and if you configure your network with BGP in a multi-homed environment, odds are good that you will want to implement this kind of filter.

• Question 2:

  R3#show run | include defaultip default-network 140.140.0.0 ip default-network 130.130.0.0 R3#show ip route | begin Gateway

  Gateway of last resort is 0.0.0.0 to network 130.130.0.0 116.0.0.0/8 is variably subnetted, 5 subnets, 3 masks C 116.16.37.0/30 is directly connected, Serial1/0.2 C 116.16.32.0/30 is directly connected, Serial2/0.2 C 116.16.34.0/28 is directly connected, Serial1/0.1 C 116.16.35.0/28 is directly connected, Serial2/0.1 S 116.0.0.0/8 [1/0] via 116.16.34.0

  *

  140.140.0.0/32 is subnetted, 3 subnets O 140.140.1.1 [110/65] via 116.16.34.4, 00:14:54, Serial1/0.1 O 140.140.3.1 [110/65] via 116.16.34.4, 00:14:54, Serial1/0.1 O 140.140.2.1 [110/65] via 116.16.34.4, 00:14:54, Serial1/0.1

  *

  130.130.0.0/16 is variably subnetted, 4 subnets, 2 masks D* 130.130.0.0/16 is a summary, 00:30:04, Null0 C 130.130.1.0/24 is directly connected, Ethernet0/0 C 130.130.2.0/24 is directly connected, Ethernet0/1 C 130.130.3.0/24 is directly connected, Ethernet1/0 D 150.150.0.0/16 [90/679936] via 116.16.35.5, 00:02:58, Serial2/0.1

  Refer to the exhibit. Why is the 140.140.0.0 network not used as the gateway of last resort even though it is configured first?

  A. The last default-network statement will always be preferred.
  B. A route to the 140.140.0.0 network does not exist in the routing table.
  C. Default-network selection will always prefer the statement with the lowest IP address.
  D. A router will load balance across multiple default-networks; repeatedly issuing the show ip route command would show the gateway of last resort changing between the two networks.
  B. A route to the 140.140.0.0 network does not exist in the routing table.

  ---

  As you can see in the exhibit, 140.140.0.0 doesn't appear in the routing table.

• Question 3:

  Which BGP attribute is used by BGP to prevent routing loops?

  A. AS-path
  B. next-hop
  C. MED
  D. weight
  E. local preference
  F. origin
  A. AS-path

  ---

  The AS-PATH attribute is used to prevent BGP routing loops. When receiving an BGP advertisement, the router checks the AS-PATH attribute, if it see it's own AS number in the AS-Path then it is a routing loop so the router will not install this route in its BGP table.

• Question 4:

  Refer to the exhibit. Will redistributed RIP routes from OSPF Area 2 be allowed in Area 1?

  

  A. Because Area 1 is an NSSA, redistributed RIP routes will not be allowed.
  B. Redistributed RIP routes will be allowed in Area 1 because they will be changed into type 5 LSAs in Area 0 and passed on into Area 1.
  C. Because NSSA will discard type 7 LSAs, redistributed RIP routes will not be allowed in Area 1.
  D. Redistributed RIP routes will be allowed in Area 1 because they will be changed into type 7 LSAs in Area 0 and passed on into Area 1.
  E. RIP routes will be allowed in Area 1 only if they are first redistributed into EIGRP.
  A. Because Area 1 is an NSSA, redistributed RIP routes will not be allowed.

  ---

  The following are several area types that are possible on OSPF: Standard area A standard area can accept link updates and route summaries. Backbone area (transit area) When interconnecting multiple areas, the backbone area is the central entity to which all other areas connect. The backbone area is always Area 0. All other areas must connect to this area to exchange route information. The OSPF backbone has all the properties of a standard OSPF area. Stub area A stub area is an area that does not accept information about routes external to the autonomous system, the OSPF internetwork, such as routes from non- OSPF sources. If routers need to reach networks outside the autonomous system, they use a default route. A default route is noted as 0.0.0.0/0. Totally stubby area A totally stubby area is an area that does not accept external autonomous system (AS) routes and summary routes from other areas internal to the autonomous system. Instead, if the router needs to send a packet to a network external to the area, it sends it using a 0.0.0.0/0 default route. Totally stubby areas are a Cisco proprietary feature. Not-so-stubby area (NSSA) An NSSA is an area that is similar to a stub area but allows for importing external routes as Type 7 LSAs and translation of specific Type 7 LSA routes into Type 5 LSAs.

• Question 5:

  After implementing EIGRP on your network, you issue the show ip eigrp traffic command on router C. The following output is shown:

  RouterC#show ip eigrp traffic IP-EIGRP Traffic Statistics for process 1 Hellos sent/received: 2112/2076 Updates sent/received: 47/38 Queries sent/received: 5/3 Replies sent/received: 3/4 Acks sent/received: 29/33 Input queue high water mark 2, 0 drops SIA-Queries sent/received: 0/0 SIA-Replies sent/received: 0/0

  Moments later, you issue the same command a second time and the following output is shown:

  RouterC#show ip eigrp traffic IP-EIGRP Traffic Statistics for process 1 Hellos sent/received: 2139/2104 Updates sent/received: 50/39 Queries sent/received: 5/4 Replies sent/received: 4/4 Acks sent/received: 31/37 Input queue high water mark 2, 0 drops SIA-Queries sent/received: 0/0 SIA-Replies sent/received: 0/0

  Moments later, you issue the same command a third time and the following output is shown:

  RouterC#show ip eigrp traffic IP-EIGRP Traffic Statistics for process 1 Hellos sent/received: 2162/2126 Updates sent/received: 53/42 Queries sent/received: 5/5 Replies sent/received: 5/4 Acks sent/received: 35/41 Input queue high water mark 2, 0 drops SIA-Queries sent/received: 0/0 SIA-Replies sent/received: 0/0

  What information can you determine about this network?

  A. The network is stable.
  B. There is a flapping link or interface, and router C knows an alternate path to the network.
  C. There is a flapping link or interface, and router C does not know an alternate path to the network.
  D. EIGRP is not working correctly on router C.
  E. There is not enough information to make a determination.
  B. There is a flapping link or interface, and router C knows an alternate path to the network.

  ---

  We notice that the "Queries received" number is increased so router C has been asked for a route. The "Replies sent" number is also increased -> router C knows an alternate path to the network.

• Question 6:

  A network administrator uses GRE over IPSec to connect two branches together via VPN tunnel. Which one of the following is the reason for using GRE over IPSec?

  A. GRE over IPSec provides better QoS mechanism and is faster than other WAN technologies.
  B. GRE over IPSec decreases the overhead of the header.
  C. GRE supports use of routing protocol, while IPSec supports encryption.
  D. GRE supports encryption, while IPSec supports use of routing protocol.
  C. GRE supports use of routing protocol, while IPSec supports encryption.

  ---

  Reference: http://www.dslreports.com/faq/8228 (4th para)

• Question 7:

  Refer to the exhibit.

  

  ROUTE.com has just implemented this EIGRP network. A network administrator came to you for advice while trying to implement load balancing across part of their EIGRP network. If the variance value is configured as 2 on all routers and all other metric and K values are configured to their default values, traffic from the Internet to the data center will be load balanced across how many paths?

  A. 1
  B. 2
  C. 3
  D. 4
  E. 5
  C. 3

  ---

  First we should list all the paths from the Internet to the data center:

  +

  A-B-C-H with a metric of 70 (40 + 15 + 15)

  +

  A-B-E-H with a metric of 60 (40+10+10)

  +

  A-D-E-H with a metric of 30 (10+10+10)

  +

  A-D-E-B-C-H with a metric of 60 (10+10+10+15+15)

  +

  A-D-E-F-G-H with a metric of 70 (10+10+10+20+20)

  +

  A-F-G-H with a metric of 60 (20+20+20)

  +

  A-F-E-H with a metric of 40 (20+10+10)

  So the path A-D-E-H will be chosen because it has the best metric. But EIGRP can support unequal cost path load balancing. By configuring the variance value of 2, the minimum metric is increased to 60 (30 * 2) and all the routes that have a metric of less than or equal to 60 and satisfy the feasibility condition will be used to send traffic.

  Besides the main path A-D-E-H we have 4 more paths that have the metric of less than or equal to 60 (we also include the Advertised Distances of these routes for later comparison):

  +

  A-B-E-H with an AD of 20

  +

  A-D-E-B-C-H with an AD of 50

  +

  A-F-G-H with an AD of 40

  +

  A-F-E-H with an AD of 20

  Now the last thing we need to consider is the feasible condition. The feasible condition states:

  "To qualify as a feasible successor, a router must have an AD less than the FD of the current successor route"

  The FD of the current successor route here is 30 (notice that the variance number is not calculated here). Therefore there are only 2 paths that can satisfy this conditions: the path A- B-E-H and A-F-E-H.

  In conclusion, traffic from the Internet to the data center will be load balanced across 3 paths, including the main path (successor path)

• Question 8:

  Refer to the exhibit.

  

  Which router configuration command can be given that will restrict router RTB from sharing its routing information with router RTA?

  A. the eigrp stub command on router RTA
  B. the eigrp stub command on router RTB
  C. the eigrp stub connected command on router RTA
  D. the eigrp stub connected command on router RTB
  E. the eigrp stub receive-only command on router RTA
  F. the eigrp stub receive-only command on router RTB
  F. the eigrp stub receive-only command on router RTB

  ---

  This is a hub and spoke network, so EIGRP stub receive-only command on RTB will restrict the router from sharing its routing information with RTA.

• Question 9:

  Which three statements about the EIGRP routing protocol are true? (Choose three)

  A. EIGRP supports five generic packet types, including Hello, Database Description (DBD), Linkstate Request (LSR), Link-State Update (LSU), and LSAck.
  B. EIGRP sends periodic hello packets to the multicast IP address 224.0.0.10.
  C. EIGRP will not form a neighbor relationship with another peer when their AS number and K values, either or both are mismatched.
  D. EIGRP sends periodic hello packets to the multicast IP address 224.0.0.9.
  E. EIGRP will form a neighbor relationship with another peer even when their K values are mismatched.
  F. EIGRP supports five generic packet types, including Hello, Update, Query, Reply, and ACK packets.
  B. EIGRP sends periodic hello packets to the multicast IP address 224.0.0.10.
  C. EIGRP will not form a neighbor relationship with another peer when their AS number and K values, either or both are mismatched.
  F. EIGRP supports five generic packet types, including Hello, Update, Query, Reply, and ACK packets.

  ---

  Reference: http://www.ietf.org/id/draft-savage-eigrp-00.txt (see eigrp packets) http://www.ciscopress.com/articles/article.asp?p=27839

• Question 10:

  Which three statements about configuring OSPF in a IPv6 network are true? (Choose three.)

  A. OSPF version 2 will support IPv6.
  B. OSPF version 3 will support IPv6.
  C. Multiple instances of OSPF for IPv6 can be run on a link.
  D. Networks must be explicitly configured using the network command in router OSPF configuration mode.
  E. IPv4 addresses cannot be used as the router ID in OSPF for IPv6.
  F. The interface command ipv6 ospf area is all that is required to enable OSPF for IPv6 on an interface.
  B. OSPF version 3 will support IPv6.
  C. Multiple instances of OSPF for IPv6 can be run on a link.
  F. The interface command ipv6 ospf area is all that is required to enable OSPF for IPv6 on an interface.

  ---

  Reference: http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-ospf.html