Cisco 642-902 Online Practice Questions and Exam Preparation

Cisco 642-902 Online Questions & Answers

• Question 221:

  You are a network technician, study the exhibit carefully.

  

  What must be done on router A in order to make EIGRP work effectively in a Frame Relay multipoint environment?

  A. Issue the command bandwidth 56 on the physical interface.
  B. Issue the command bandwidth 56 on each subinterface.
  C. Issue the command bandwidth 224 on each subinterface.
  D. Issue the command bandwidth 224 on the physical interface.
  D. Issue the command bandwidth 224 on the physical interface.

  ---

  In Frame Relay, all neighbors share the same bandwidth, regardless of the actual CIR of each individual PVC. In this case the CIR of each PVC is the same so we can find the bandwidth of the main interface (multipoint connection interface) by 56 x 4 = 224.

  Notice that if the bandwidth on each PVC is not equal then we get the lowest bandwidth to multiply.

• Question 222:

  Refer to the exhibit.

  

  The partial configuration for an OSPF ASBR and an Area 0 ABR is shown. Assume the OSPF configurations throughout the network are operable. Which statement about these configurations is true?

  A. The ASBR route-maps are basically useless, because there are no deny prefix-lists.
  B. LSA Type 5s will not be received by the ABR from the ASBR.
  C. The OSPF backbone will not learn any RFC 1918 addresses.
  D. The matched prefix-list addresses will be given a metric of 255, which is essentially unreachable.
  C. The OSPF backbone will not learn any RFC 1918 addresses.

  ---

  The ASBR accepts RFC 1918 addresses and set these networks to "tag 255 but when advertising into Area 0, the ABR Area 0 filters out these networks because they match "tag 255 so the OSPF backbone will not learn any RFC 1918 addresses.

  Note that if you use an ACL in a route-map deny clause, routes that are permitted by the ACL are not redistributed. All the networks with "tag 255 are blocked by the clause 10 while all other networks are permitted by the clause 20 of the route-map (if a match command is not present, all routes match the clause).

  Note:

  RFC 1918 addresses include:

  +

  Class A: 10.0.0.0 10.255.255.255 (10/8 prefix)

  +

  Class B: 172.16.0.0 172.31.255.255 (172.16/12 prefix) + Class C: 192.168.0.0 192.168.255.255 (192.168/16 prefix)

• Question 223:

  A router has two paths to reach another network in a different autonomous system. Neither route was generated by the local router and both routes have the same default weight and local preference values. Which statement is true about how BGP would select the best path?

  A. If the command bgp always-compare-med has been given, then the router will prefer the route with the highest MED.
  B. The router will prefer the route with the lower MED.
  C. The router will prefer the shortest autonomous system path.
  D. To influence one route to be preferred, its default local preference value will be changed via the use of the command bgp default local-preference 50.
  C. The router will prefer the shortest autonomous system path.

  ---

  In the Route selection decision process, if the weight, local preference and route originated are the same then the shortest AS path will be chosen.

  The full Route selection decision process is listed below:

  1.

  Prefer highest weight (local to router)

  2.

  Prefer highest local preference (global within AS)

  3.

  Prefer route originated by the local router (next hop = 0.0.0.0)

  4.

  Prefer shortest AS path

  5.

  Prefer lowest origin code (IGP < EGP )

  6.

  Prefer lowest MED (exchanged between autonomous systems)

  7.

  Prefer EBGP path over IBGP path

  8.

  Prefer the path through the closest IGP neighbor (IGP cost)

  9.

  Prefer oldest route for EBGP paths

  10.

  Prefer the path with the lowest neighbor BGP router ID

  11.

  Prefer the path with the lowest neighbor IP address Reference: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml

• Question 224:

  You want the redistributed EIGRP AS 10 routes to have an administrative distance of 121 when they appear as RIP routes in the routing table of A1. Which command should you use on a router to accomplish this goal?

  

  A. redistribute eigrp 10 metric 121
  B. redistribute rip metric 121
  C. default-metric 121
  D. distance 121 10.1.1.6 0.0.0.0
  D. distance 121 10.1.1.6 0.0.0.0

  ---

  If you add that route back with an administrative distance of 121, the ASA will still prefer the route learned via RIP because it prefers the route with a lower administrative distance.

• Question 225:

  Refer to the exhibit.

  

  Router RT-1 chooses one path to network 198.133.219.0/24. Indicate the reason Router RT-1 chooses this "best" path.

  A. In making its decision about the best path, RT-1 gives precedence to the origin code.
  B. In making its decision about the best path, RT-1 gives precedence to the BGP MED values.
  C. IP address 128.107.2.2 is lower than 128.107.255.2.
  D. In making its decision about the best path, RT-1 prefers the IGP metrics.
  E. RT-1 prefers internal BGP routes.
  F. IP address 128.107.254.2 is lower than 128.107.255.2.
  A. In making its decision about the best path, RT-1 gives precedence to the origin code.

  ---

  After BGP receives updates about different destinations from different autonomous systems, it chooses the best path to reach a specific destination. The following process summarizes how BGP chooses the best route on a Cisco router.

  Prefer the route with the highest weight. (The weight attribute is proprietary to Cisco and is local to the router only.)

  If multiple routes have the same weight, prefer the route with the highest local preference value. (The local preference is used within an autonomous system.) If multiple routes have the same local preference, prefer the route that the local

  router originated. A locally originated route has a next hop of 0.0.0.0 in the BGP table. If none of the routes were locally originated, prefer the route with the shortest autonomous system path. If the autonomous system path length is the same,

  prefer the lowest origin code (IGP < EGP < incomplete). If all origin codes are the same, prefer the path with the lowest MED. (The MED is exchanged between autonomous systems.) The MED comparison is made only if the neighboring

  autonomous system is the same for all routes considered, unless the bgp always-compare-med command is enabled If the routes have the same MED, prefer external paths to internal paths. If synchronization is disabled and only internal

  paths remain, prefer the path through the closest IGP neighbor, which means that the router prefers the shortest internal path within the autonomous system to reach the destination (the shortest path to the BGP next hop).

  For EBGP paths, select the oldest route to minimize the effect of routes going up and down (flapping). Prefer the route with the lowest neighbor BGP router ID value. If the BGP router IDs are the same, prefer the router with the lowest

  neighbor IP address.

• Question 226:

  Which statement is true about OSPF Network LSAs?

  A. They are originated by every router in the OPSF network. They include all routers on the link, interfaces, the cost of the link, and any known neighbor on the link.
  B. They are originated by the DR on every multi-access network. They include all attached routers including the DR itself.
  C. They are originated by Area Border Routers and are sent into a single area to advertise destinations outside that area.
  D. They are originated by Area Border Router and are sent into a single area to advertise an Autonomous System Border Router.
  B. They are originated by the DR on every multi-access network. They include all attached routers including the DR itself.

  ---

  The point of this question is OSPF Network LSAs

  The feature of OSPF Network LSAs is that they are generated by DR, and DR only exist on multi-access network, the use of OSPF Network LSAs is that it list all neighbors around and send it to every router which run OSPF.

  Incorrect Answer: OSPF Network LSAs are not originated by Area Border Routers.

• Question 227:

  Refer to the exhibit.

  

  A company would prefer all Internet-bound OSPF routed traffic to use ISP ABC with ISP DEF as a backup. As the network consultant, what three configuration changes should you make? (Choose three.)

  A. The default-information originate command should be configured on router B1 and B4.
  B. The default-information originate command should be configured on router B2 and B3.
  C. If the metric value for ISP ABC is set at the default, the ISP DEF metric value should be set to 1.
  D. If the metric value for ISP ABC is set at the default, the ISP DEF metric value should be set to 25.
  E. The metric type value should be set to type 1.
  F. The metric type value should be set to type 2.
  B. The default-information originate command should be configured on router B2 and B3.
  D. If the metric value for ISP ABC is set at the default, the ISP DEF metric value should be set to 25.
  F. The metric type value should be set to type 2.

  ---

  Routers B2 and B3 need to advertise a default route to the Internet for "inside" OSPF routers so we should use the "default-information originate" command with a default route (something like "ip route 0.0.0.0 0.0.0.0 ") pointing to the ISP router. If no metric is specified, OSPF puts a default value of 20 when redistributing routes from all protocols except BGP routes (BGP routes get a metric of 1). We use ISP DEF as a backup so its metric value should be set to a higher value than 20. There are two types of external routes: external type 1 and external type 2. The difference between the two is in the way the cost (metric) of the route is being calculated:

  + The cost of a type 2 route is always the external cost, irrespective of the interior cost to reach that route. + Type 1 cost is the addition of the external cost and the internal cost used to reach that route.

  -> We should configure the type 2 external route to make sure the ISP ABC is always referred over ISP DEF because internal routing does not determine the path. Note: E2 is the default external metric, but E1 is preferred over E2 if two equal-cost paths exist.

• Question 228:

  Which three restrictions apply to OSPF stub areas? (Choose three.)

  A. No virtual links are allowed.
  B. The area cannot be a backbone area.
  C. Redistribution is not allowed unless the packet is changed to a type 7 packet.
  D. The area has no more than 10 routers.
  E. No Autonomous System Boundary Routers are allowed.
  F. Interarea routes are suppressed.
  A. No virtual links are allowed.
  B. The area cannot be a backbone area.
  E. No Autonomous System Boundary Routers are allowed.

  ---

  Reference: http://www.juniper.net/techpubs/en_US/junos13.1/topics/concept/ospf-routing- understanding-ospf-areas-overview.html (see stub areas)

• Question 229:

  Refer to the exhibit.

  

  EIGRP is configured on all routes in the network. On a basis of the show ip eigrp topology output provided, what conclusion can be derived?

  A. Router R1 can send traffic destined for network 10.6.1.0/24 out of interface FastEthernet0/0
  B. Router R1 is waiting for a reply from the neighbor 10.1.2.1 to the hello message sent out before it declares the neighbor unreachable
  C. Router R1 is waiting for a reply from the neighbor 10.1.2.1 to the hello message sent out inquiring for a second successor to network 10.6.1.0/24
  D. Router R1 is waiting for a reply from the neighbor 10.1.2.1 in response to the query sent about network 10.6.1.0/24
  D. Router R1 is waiting for a reply from the neighbor 10.1.2.1 in response to the query sent about network 10.6.1.0/24

  ---

  The "show ip eigrp topology" command lists all routes that EIGRP is aware of and shows whether EIGRP is actively processing information on that route. Under most normal conditions, the routes should all be in a passive state and no EIGRP

  process are running for that route. If the routes are active, this could indicate the dreaded stuck in active, or SIA, state.

  The fields to note in this output are as follows:

  P-- Passive; no EIGRP computation is being performed. This is the ideal state. A-- Active; EIGRP computations are "actively" being performed for this destination. Routes constantly appearing in an active state indicate a neighbor or query

  problem.

  Both are symptoms of the SIA problem.

  U-- Update; an update packet was sent to this destination. Q-- Query; a query packet was sent to this destination. R-- Reply; a reply packet was sent to this destination. Route information-- IP address of the route or network, its subnet mask, and the successor, or next hop to that network, or the feasible successor.

• Question 230:

  Based on the need to limit processing and bandwidth utilization due to dynamic routing protocol operation, the following routing requirements have been specified for your network.

  -Partial and incremental routing updates

  - Only the devices affected by a topology change perform route recomputation

  -Route recomputation only occurs for routes that were affected

  Which dynamic routing protocol should be deployed in your network to best meet these requirements?

  A. BGP
  B. OSPF
  C. IS-IS
  D. EIGRP
  E. RIPv2
  D. EIGRP

  ---

  The bandwidth utilization issue has been addressed by implementing partial and incremental updates. Therefore, only when a topology change occurs does routing information get sent. Regarding processor utilization, the feasible successor

  technology greatly reduces the total processor utilization of an AS by requiring only the routers that were affected by a topology change to perform the route recomputation. Furthermore, the route recomputation only occurs for routes that

  were affected. Only those data structures are accessed and used. This greatly reduces search time in complex data structures.

  Reference:

  http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f07.shtml (See frequently asked questions)