Cisco CCNP 300-410 Questions & Answers

• Question 11:

  

  Router R2 operates in a broadcast, multi-access network. Examine the following output of the show ip ospf neighbor command.

  Based on the output, with which routers can R2 establish a full adjacency?

  A. the neighbor at 192.168.5.6

  B. the neighbor at 192.168.5.10

  C. the neighbor at 192.168.5.116

  D. the neighbor at 192.168.5.107

  Correct Answer: D

  R2 can establish a full adjacency with the neighbor at 192.168.5.107 and the neighbor at 192.168.5.165. In a broadcast, multi-access network OSPF network, full adjacencies can only be established with a designated router (DR) or a backup

  designated router (BDR).

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify OSPF neighbor relationship and authentication

  References:

  Home.Support > Technology Support > IP > IP Routing > Design > Design Technotes > What does the show ip ospf neighbors command reveal? Cisco > Cisco IOS IP Routing: OSPF Command Reference > show ip ospf neighbor

• Question 12:

  Examine the following diagram:

  

  Which of the following actions will make area 1 a totally stubby area? (Choose all that apply. Each correct answer is part of the solution.)

  A. execute the area 1 stub no-summary command on RouterA

  B. execute the area 1 stub no-summary command on RouterB

  C. execute the area 1 stub command on RouterB

  D. execute the area 1 stub command on RouterA

  E. execute the area 0 stub-no summary command on RouterA

  F. execute the area 0 stub no-summary command on RouterB

  G. execute the area 0 stub command on RouterB

  H. execute the area 0 stub command on RouterA

  Correct Answer: AC

  You should execute the area 1 stub no-summary command on RouterA and the area 1 stub command on RouterB. A totally stubby area is one that only keeps local area routes in the link-state database (LSDB), plus a default route that leads

  out of the area. To make an area totally stubby, the area border router (ABR) should be configured with the area 1 stub no-summary command and all other area routers should be configured with the area 1 stub command. The diagram in the

  scenario indicates that RouterA is the border router. You should not run any of the commands that refer to area 0. This would affect a different area than the requirement stated in the scenario.

  None of the other combinations of actions will create a totally stubby area.

  If you run the area 1 stub command on both RouterA and RouterB, it will create a stub area. A stub area differs from a totally stubby area in that a stub area will allow updates about areas in the same OSPF domain.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify network types, area types, and router types

  References:

  Cisco > Home > Support > Technology Support > IP > IP Routing > Design > Design Technotes > What Are OSPF Areas and Virtual Links? > Define a Totally Stub Area

• Question 13:

  Which command is the proper command for allowing RIP routing updates to be received on an interface while not allowing them to be sent out of the same interface?

  A. Router(config)# passive-interface e0/0

  B. Router(config-if)# passive-interface

  C. Router(config-if)# interface passive

  D. Router(config-router)# passive-interface e0/0

  E. Router(config-router)# interface passive e0/0

  Correct Answer: D

  The correct answer is as follows:

  Router(config-router)# passive-interface e0/0

  The effect of the passive-interface command is dependent on the routing protocol running on the interface. For EIGRP, the router will not only stop sending routing updates, but also hellos, which means that it will not form a neighbor

  relationship with another EIGRP router on that interface. This is also the case with OSPF and IS-IS. With RIP, however, the router will continue to send hellos even as it stops sending routing updates, and it will still receive routing updates.

  The passive-interface command issued at the router configuration mode will prevent routing updates from being sent out on a specific interface while still allowing the interface to receive updates. This command can be used in any situation

  where you want the router to receive routing updates on a particular interface but not send any updates. This is helpful for security purposes, for preventing routing loops, or to control routing update traffic.

  The other options either use improper syntax or are executed at an incorrect prompt.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify loop prevention mechanisms

  References:

  Cisco > Home > Support > Technology Support > IP > IP Routing > Design > Design Technotes > How Does the Passive Interface Feature Work in EIGRP? Cisco > Cisco IOS IP Routing: Protocol-Independent Command Reference >

  passive-interface

• Question 14:

  You manage the EIGRP subnet in your organization. You have enabled EIGRP for IPv6 on all the routers in the EIGRP AS 355 using the following commands on all the routers: The ipv6 unicast-routing command in global configuration mode The interface command in global configuration mode The ipv6 enable command in interface configuration mode The ipv6 eigrp command in interface configuration mode The ipv6 router eigrp command in global configuration mode The eigrp router-id command in global configuration mode During verification, you discover that EIGRP for IPv6 is not running on the routers. Which of the following should be done to fix the issue?

  A. The ipv6 address command should be executed in interface configuration mode.

  B. The ipv6 address command should be executed in router configuration mode.

  C. The eigrp router-id command should be executed in interface configuration mode.

  D. The eigrp router-id command should be executed in router configuration mode.

  Correct Answer: D

  The eigrp router-id command should be executed in router configuration mode to fix the issue. This command specifies a fixed router IPv4 address to the router. If this command is missing or incorrectly configured on the router, EIGRP for

  IPv6 will not run properly.

  Another command that you should perform so that EIGRP for IPv6 runs on the routers is the no shutdown command. You should execute this command in interface configuration mode. The no shutdown command is necessary because all

  the interfaces with EIGRP for IPv6 enabled on them are in a shutdown state by default.

  A sample configuration to implement EIGRP for IPv6 on a router is as follows:

  rtrA(config)# ipv6 unicast-routing

  rtrA(config) # interface Fa0/1

  rtrA(config-if) # ipv6 enable

  rtrA(config-if) # ipv6 eigrp 355

  rtrA(config-if)# no shutdown

  rtrA(config-if) # exit

  rtrA(config)# ipv6 router eigrp 355

  rtrA(config-rtr)# eigrp router-id 1.1.1.1

  The two options stating that the ipv6 address command should be executed on the routers are incorrect. EIGRP for IPv6 can be configured on router interfaces without explicitly specifying a global unicast IPv6 address. If you specify the ipv6

  enable command, as in this scenario, then the ipv6 address command is not required.

  The option stating that the eigrp router-id command should be executed in interface configuration mode is incorrect. This command should be executed in router configuration mode instead of interface or global configuration modes.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Identify IPv6 addressing and subnetting

  References:

  Cisco IPv6 Implementation Guide, Release 15.2MandT > Implementing EIGRP for IPv6 > How to Implement EIGRP for IPv6 > Enabling EIGRP for IPv6 on an Interface

• Question 15:

  Router 5 has four interfaces. The networks hosted on each interface are as follows:

  Fa0/1 192.168.5.4/29 Fa0/2 192.168.6.0/24 Fa0/3 192.168.7.0/24 S0/0 172.16.5.0/24

  You execute the following commands on the router:

  

  After this command sequence is executed, what routes will be present in the routing table of the router at 172.16.5.2? (Choose all that apply.)

  A. 192.168.5.4/29

  B. 172.16.5.0/24

  C. 192.168.6.0/24

  D. 192.168.7.0/24

  E. none of these will be present

  F. only network addresses beginning with 192 will be present

  Correct Answer: ABCD

  Despite the inclusion of the command aggregate-address 192.168.5.0 255.255.252.0, all subnets of the aggregate route will also be placed in the routing updates because of the omission of the summary-only keyword. Therefore,

  192.168.5.4/29, 172.16.5.0/16, 192.168.6.0/24 and 192.168.7.0/24 will be present.

  Had the following command been executed, the subnet addresses would not appear in the routing table of the router at 172.16.5.2:

  Router5(config-router)# aggregate-address 192.168.5.0 255.255.252.0 summary-only

  Therefore, both the aggregate address and all of the 192.168.0.0 subnets will be in the routing table.

  The 172.16.5.0/24 network will be in the routing table of the router at 172.160.5.1 because it is directly connected.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify manual and autosummarization with any routing protocol

  References:

  Cisco > Cisco IOS IP Routing: BGP Command Reference > aggregate-address

• Question 16:

  Consider the following output of the show ip bgp summary command:

  

  Which of the following neighbors have an established connection with RouterA?

  A. 10.1.1.1

  B. 10.2.1.1

  C. 10.3.1.1

  D. 10.4.1.1

  E. 10.5.1.1

  Correct Answer: B

  The neighbor with the IP address 10.2.1.1 has an established connection with RouterA. This is because the State/PfxRcd value for this neighbor is a number, 15, which indicates the number of prefixes received by RouterA from the neighbor.

  The prefixes are exchanged between BGP neighbors through the update message, which can be transmitted only if an established connection exists between the neighbors. An established connection exists between two neighbors if the local

  router is in Open Confirm state and it receives a KEEPALIVE or an UPDATE message.

  The connection between RouterA and the neighbor with the IP address 10.1.1.1 is not established. This is because the State/PfxRcd value for this neighbor is OPENSENT. In this state, RouterA sends an OPEN message to a neighbor to

  determine the parameters for establishing a connection. The OPENSENT state occurs before the connection is established.

  The connection between RouterA and the neighbor with the IP address 10.3.1.1 is not established. This is because the State/PfxRcd value for this neighbor is IDLE. In this state, RouterA does not accept any incoming connections from the

  neighbor.

  The connection between RouterA and the neighbor with the IP address 10.4.1.1 is not established. This is because the State/PfxRcd value for this neighbor is ACTIVE. In this state, RouterA is attempting to establish a BGP peering session

  but it is not yet complete.

  The connection between RouterA and the neighbor with the IP address 10.5.1.1 is not established. This is because the State/PfxRcd value for this neighbor is OPENCONFIRM. In this state, RouterA waits for a KEEPALIVE or NOTIFICATION

  message from the neighbor.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Describe, configure, and verify BGP peer relationships and authentication

  References:

  Cisco IOS IP Routing: BGP Command Reference > show ip bgp summary

• Question 17:

  Which method of advertising networks from an autonomous system into BGP can result in the most instability?

  A. Using the network command

  B. Redistributing static routes into BGP

  C. Redistributing dynamic routes into BGP

  D. Redistributing static routes into IBGP

  Correct Answer: C

  Redistributing dynamic IGP routes into BGP can result in instability, and is not recommended.

  Dynamic routes can disappear from the routing table, and even flap up and down constantly if there are link problems, especially with WAN links. If the networks are redistributed into BGP, their flapping can result in BGP updates about the

  route changing status, resulting in instability for BGP.

  Most ISPs guard against unstable routes and might threaten to cut off your BGP connectivity if you have flapping routes that cause BGP instability in their networks.

  The network command and redistributed static routes, on the other hand, tend not to change state so often. As a result, they are considered much more stable from a BGP perspective.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify manual and autosummarization with any routing protocol

  References:

  Cisco > Support > Technology Support > IP > IP Routing > Design > Design Technotes > BGP Case Studies > Document ID: 26634 > Redistribution

• Question 18:

  Examine the exhibit.

  

  You have determined that RTR2 is not advertising the CIDR summary address 192.168.0.0 to the other routers in AS 65100. Which set of configuration commands will enable the BGP router RTR2 to announce the network prefix 192.168.0.0/16 to the other routers in the AS 65100?

  A. router bgp 65100 neighbor 172.16.1.2 remote-as 65100 neighbor 192.168.3.2 remote-as 65100 network 192.168.3.0

  B. router bgp 65100 neighbor 172.16.1.2 remote-as 65101 neighbor 192.168.3.2 remote-as 65100 network 192.168.0.0

  C. router bgp 65100 neighbor 172.16.1.2 remote-as 65100 neighbor 192.168.3.2 remote-as 65100 network 192.168.0.0 mask 255.255.0.0 ip route 192.0.0.0 255.0.0.0 null 0

  D. router bgp 65100 neighbor 172.16.1.2 remote-as 65101 neighbor 192.168.3.2 remote-as 65100 network 192.168.0.0 mask 255.255.0.0 ip route 192.168.0.0 255.255.0.0 null 0

  Correct Answer: D

  Issuing the following commands will cause RTR2 to advertise the CIDR block 192.168.0.0/16 to the other routers by using BGP:

  RTR2(config)# router bgp 65100

  RTR2(config-router)# neighbor 172.16.1.2 remote-as 65101

  RTR2(config-router)# neighbor 192.168.3.2 remote-as 65100

  RTR2(config-router)# network 192.168.0.0 mask 255.255.0.0

  RTR2(config-router)# ip route 192.168.0.0 255.255.0.0 null 0

  The network command specifies the address that will be inserted into the BGP table. Without the mask keyword, the classful network will be assumed. Because 255.255.0.0, or /16, is not the natural mask for any Class C address, the mask

  keyword must also be specified. Thus, 192.168.0.0 and 255.255.0.0 identify the desired address and mask of the 192.168.0.0/16 network prefix.

  The router checks the IP forwarding table for an exact match before it advertises the route. Without a matching entry in the IP forwarding table, that route will not be advertised. RTR2 must be able to advertise a CIDR block and not the

  individual subnets. A static route is required because BGP requires that a match of the network prefix be present in the forwarding table when using the network command with the mask keyword. Therefore, to ensure an exact match for the

  identified prefix exists in the IP forwarding table, and to ensure that the prefix will always be advertised, a static route for 192.168.0.0/16 to null 0 is also required.

  The syntax for the network command is shown below:

  network network-number [ mask network-mask ] [ route-map map-tag ]

  The parameters are:

  mask - This parameter is optional and identifies the network or subnetwork to advertise. route-map - This parameter is optional and identifies a preconfigured route-map that will be used to filter specific addresses from being advertised.

  The following command set is missing the mask keyword in the network command and the command to create a static route to null 0. The address used in the network command is also incorrect. It should 192.168.0.0:

  router bgp 65100

  neighbor 172.16.1.2 remote-as 65100

  neighbor 192.168.3.2 remote-as 65100

  network 192.168.3.0

  The following command set is missing the mask keyword in the network command and the command to create a static route to null 0:

  router bgp 65100

  neighbor 172.16.1.2 remote-as 65101

  neighbor 192.168.3.2 remote-as 65100

  network 192.168.0.0

  The following command set uses an incorrect mask (255.0.0.0) in the command that creates the static route to null 0. It should be 255.255.0.0:

  router bgp 65100

  neighbor 172.16.1.2 remote-as 65100

  neighbor 192.168.3.2 remote-as 65100

  network 192.168.0.0 mask 255.255.0.0

  ip route 192.0.0.0 255.0.0.0 null 0

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Describe, configure, and verify BGP peer relationships and authentication

  References:

  Internetworking Case Studies > Using the Border Gateway Protocol for Interdomain Routing > Controlling the Flow of BGP Updates > CIDR and Aggregate Addresses > Aggregation and Static Routes

• Question 19:

  Refer to the following exhibit that shows four Cisco routers named rtr1, rtr2, rtr3, and rtr4:

  

  The routers rtr2, rtr3, and rtr4 are eBGP peers of rtr1. In addition, rtr3 and rtr4 are also eBGP peers.

  You want to implement the following requirements on rtr1:

  The first attribute to select the best path is used.

  Advertisements about 10.77.22.0/24 sent by rtr4 will be chosen over the advertisements sent by rtr3.

  Which of the following commands should be included in the implementation plan for rtr1 to achieve the desired results? (Each option is a part of the solution. Choose all that apply.)

  A. neighbor 135.90.66.1 route-map set_weight out

  B. neighbor 135.90.66.6 route-map set_weight in

  C. route-map set_weight deny 10

  D. match ip-address 1

  E. set metric 100

  F. set weight 100

  Correct Answer: BDF

  The following commands should be included in the implementation plan:

  neighbor 135.90.66.6 route-map set_weight in match ip-address 1 set weight 100

  The neighbor 135.90.66.6 route-map set_weight in command specifies a route-map named set_weight for the incoming routing updates from 135.90.66.6 peer. The match ip-address 1 command specifies a criterion to match the IP address as specified in an access list. When the match criterion is met, the action specified in the set weight command is performed.

  The set weight 100 command sets the weight attribute, which is a Cisco-defined attribute, to 100. The weight attribute is the first to be checked when BGP selects the best path between eBGP routers. This attribute is local to the router on which it is set and cannot be advertised to other routers. The complete set of commands to achieve the desired results is as follows:

  access-list 1 permit 10.77.22.0 0.0.0.255 router bgp 444 neighbor 135.90.66.3 remote-as 111 neighbor 135.90.66.1 remote-as 222 neighbor 135.90.66.6 remote-as 333 neighbor 135.90.66.6 route-map set_weight in route-map set_weight permit 10 match ip-address 1 set weight 100

  The set metric 100 command should not be included in the implementation plan to achieve the desired results. This command sets the metric to 100; however, the requirement is to use the first attribute to be checked, which is the weight

  attribute.

  The neighbor 135.90.66.1 route-map set_weight out command should not be included in the implementation plan. This command forms an eBGP neighbor relationship with rtr3. The command also uses a route map named set_weight to set

  the weight attribute for the routes sent by rtr1. However, the weight attribute is local to rtr1 and cannot be set for outbound routes.

  The route-map set_weight deny 10 command should not be specified in the implementation plan to achieve the desired results. This command creates a route map named set_weight. The deny keyword in this command indicates that if the

  match criterion is satisfied, then the set action is not performed. The permit keyword should be specified instead of the deny keyword to perform the set action when a match occurs.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Identify suboptimal routing

  References:

  Cisco > Support > Technology Support > IP > IP Routing > Design > Design Technotes > BGP Case Studies > BGP Case Studies 1 > Route Maps Cisco > Support > Technology Support > IP > IP Routing > Design > Design Technotes >

  BGP Best Path Selection Algorithm

  Cisco > Support > Technology Support > IP > IP Routing > Design > Design Technotes > BGP Case Studies > BGP Case Studies 2 > Weight Attribute

• Question 20:

  Refer to the following table:

  

  Path1, Path2, and Path3 are the available routes between routers A and B. The bgp always-compare med command is executed for all three routes.

  What should be the value for the missing ASN (represented by a question mark in the table) so that Path3 becomes the best path between routers A and B based on their MED values?

  A. 10

  B. 20

  C. 30

  D. 40

  Correct Answer: D

  The missing autonomous system number (ASN) in the AS_PATH parameter of Path3 should be 40 so that Path3 becomes the best path from A to B. BGP selects the best path by first selecting the first valid path between two routers. If other

  paths are available between the two routers, BGP compares values of various attributes to select the best available path. In this case, Path 2 is the current best path between routers A and B. The values of various parameters (listed in the

  table) are compared with Path1 and Path2.

  While comparing Path1 and Path2, the weight, LOCAL_PREF, local originate source command, length of AS_PATH, and origin type are same. Therefore, these parameters are not useful in determining the best path. However, the MED value

  of Path2 is lower than that of Path1. As a result, Path2 is selected as the best path because BGP prefers the route with the lesser MED value.

  BGP now compares the parameter values of Path 2 (the current best path) and Path3. The weight and LOCAL_PREF parameters are same for both routes. Path 2 and Path3 are both local routes originated by using the redistribute and the

  network commands, respectively. BGP prefers local routes learned by the network or redistribute commands over those that are learned by the aggregate-address command.

  The AS_PATH parameter specifies the list of AS numbers that comprise the route. The best path should have the shortest value for the AS_PATH parameter. In this case, both Path2 and Path3 consist of three AS numbers and are originated

  by an IGP. Therefore, the AS_PATH and the origin type parameters are not helpful in determining the best path.

  Finally, BGP compares the MED values of Path2 and Path3. The MED values are compared only when the first AS number in the AS_PATH is the same for both routes; that is, when both routes begin in the same AS. The first ASN in the

  AS_PATH parameter of Path2 is 40; therefore, the missing ASN for Path3 should be 40. This allows the comparison of MED values and the selection of Path3 as the best route as it has lower MED value.

  All the other options are incorrect because a value other than 40 disables the comparison of the MED values between Path2 and Path3. If the MED value is not considered, then BGP determines whether Path3 is an iBGP or eBGP router.

  BGP selects an iBGP route instead of an eBGP route.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Explain BGP attributes and best-path selection

  References:

  Internetworking Technology Handbook > BGP > BGP attributes