Ensurepass

 

QUESTION 121

Refer to the exhibit. What is the meaning of the asterisk (*) in the output?

 

clip_image001

 

A.

PIM neighbor 10.1.5.6 is the RPF neighbor for the group 232.1.1.1 for the shared tree.

B.

PIM neighbor 10.1.5.6 is the one that is seen as the RPF neighbor when performing the command show ip rpf 10.1.4.7.

C.

PIM neighbor 10.1.5.6 is the winner of an assert mechanism.

D.

The RPF neighbor 10.1.5.6 is invalid.

 

Correct Answer: C

Explanation:

show ip mroute Field Descriptions

Field

Description

 

RPF neighbor or RPF nbr

IP address of the upstream router to the source. Tunneling indicates that this router is sending data to the RP encapsulated in register packets. The hexadecimal number in parentheses indicates to which RP it is registering. Each bit indicates a different RP if multiple RPs per group are used. If an asterisk (*) appears after the IP address in this field, the RPF neighbor has been learned through an assert.

Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/ipmulti/command/reference/fiprmc_r/1rfmult3.html

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

QUESTION 122

Refer to the exhibit. What is the role of this multicast router?

 

clip_image003

 

A.

a first-hop PIM router

B.

a last-hop PIM router

C.

a PIM rendezvous point

D.

a PIM inter-AS router

 

Correct Answer: C

Explanation:

The following is sample output from the show ip pim tunnel taken from an RP. The output is used to verify the PIM Encap and Decap Tunnel on the RP:

Switch# show ip pim tunnel

 

Tunnel0

Type : PIM Encap

RP : 70.70.70.1*

Source. 70.70.70.1

Tunnel1*

Type : PIM Decap

RP : 70.70.70.1*

Source. -R2#

 

The asterisk (*) indicates that the router is the RP. The RP will always have a PIM Encap and Decap Tunnel interface.

 

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3650/software/release/3se/multicast/co mmand_reference/b_mc_3se_3650_cr/b_mc_3se_3650_cr_chapter_010.html#wp1286920037

 

 

 

 

 

 

 

 

 

 

 

 

 

 

QUESTION 123

Refer to the exhibit. Which option explains why the forwarding address is set to 0.0.0.0 instead of 110.100.1.1?

 

clip_image005

 

A.

The interface Ethernet0/1 is in down state.

B.

The next-hop ip address 110.100.1.1 is not directly attached to the redistributing router.

C.

The next-hop interface (Ethernet0/1) is specified as part of the static route command; therefore, the forwarding address is always set to 0.0.0.0.

D.

OSPF is not enabled on the interface Ethernet0/1.

 

Correct Answer: D

Explanation:

From the output of the “show ip ospf database” command (although this command is not shown) we can conclude this is an ASBR (with Advertising Router is itself) and E0/1 is the ASBR’s next hop interface for other routers to reach network 192.168.10.0.

 

The Forwarding Address is determined by these conditions:

* The forwarding address is set to 0.0.0.0 if the ASBR redistributes routes and OSPF is not enabled on the next hop interface for those routes.

* These conditions set the forwarding address field to a non-zero address:

+ OSPF is enabled on the ASBR’s next hop interface AND + ASBR’s next hop interface is non-passive under OSPF AND + ASBR’s next hop interface is not point-to-point AND

+ ASBR’s next hop interface is not point-to-multipoint AND + ASBR’s next hop interface address falls under the network range specified in the router ospf command.

* Any other conditions besides these set the forwarding address to 0.0.0.0.

-> We can see E0/1 interface is not running OSPF because it does not belong to network 110.110.0.0 0.0.255.255 which is declared under OSPF process -> F.A address is set to 0.0.0.0. Reference: http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13682-10.html

 

 

QUESTION 124

Refer to the exhibit. You have configured two routing protocols across this point-to-point link. How many BFD sessions will be established across this link?

 

clip_image006

 

A.

three per interface

B.

one per multicast address

C.

one per routing protocol

D.

one per interface

 

Correct Answer: D

Explanation:

Cisco devices will use one Bidirectional Forwarding Detection (BFD) session for multiple client protocols in the Cisco implementation of BFD for Cisco IOS Releases 12.2(18)SXE, 12.0(31)S, and 12.4(4)T. For example, if a network is running OSPF and EIGRP across the same link to the same peer, only one BFD session will be established, and BFD will share session information with both routing protocols.

Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/fs_bfd.html#wp1053749

 

 

QUESTION 125

Refer to the exhibit. Which statement is true?

 

clip_image008

 

A.

2001:DB8::1/128 is a local host route, and it can be redistributed into a dynamic routing protocol.

B.

2001:DB8::1/128 is a local host route, and it cannot be redistributed into a dynamic routing protocol.

C.

2001:DB8::1/128 is a local host route that was created because ipv6 unicast-routing is not enabled on this router.

D.

2001:DB8::1/128 is a route that was put in the IPv6 routing table because one of this router’s loopback interfaces has the IPv6 address 2001:DB8::1/128.

 

Correct Answer: B

Explanation:

The local routes have the administrative distance of 0. This is the same adminstrative distance as connected routes. However, when you configure redistributed connected under any routing process, the connected routes are redistributed, but the local routes are not. This behavior allows the networks to not require a large number of host routes, because the networks of the interfaces are advertised with their proper masks. These host routes are only needed on the router that owns the IP address in order to process packets destined to that IP address. It is normal for local host routes to be listed in the IPv4 and IPv6 routing table for IP addresses of the router’s interfaces. Their purpose is to create a corresponding CEF entry as a receive entry so that the packets destined to this IP address can be processed by the router itself. These routes cannot be redistributed into any routing protocol.

Reference: http://www.cisco.com/c/en/us/support/docs/ip/ip-routing/116264-technote-ios-00.html

 

 

QUESTION 126

Refer to the exhibit. Routers R1, R2, and R3 are configured as shown, and traffic from R2 fails to reach 172.29.168.3. Which action can you take to correct the problem?

 

clip_image010

 

A.

Correct the static route on R1.

B.

Correct the default route on R2.

C.

Edit the EIGRP configuration of R3 to enable auto-summary.

D.

Correct the network statement for 172.29.168.3 on R3.

 

Correct Answer: A

Explanation:

On R1 we see there is a wrongly configured static route: ip route 172.29.168.3 255.255.255.255 172.17.17.2. It should be ip route 172.29.168.3 255.255.255.255 10.17.12.3.

 

 

QUESTION 127

Refer to the exhibit. R3 prefers the path through R1 to reach host 10.1.1.1. Which option describes the reason for this behavior?

 

clip_image012

 

A.

Th
e OSPF reference bandwidth is too small to account for the higher speed links through R2.

B.

The default OSPF cost through R1 is less than the cost through R2.

C.

The default OSPF cost through R1 is more than the cost through R2.

D.

The link between R2 and R1 is congested.

 

Correct Answer: A

Explanation:

The default formula to calculate OSPF bandwidth is BW = Bandwidth Reference / interface bandwidth [bps] = 10^8 / / interface bandwidth [bps]

BW of the R1-R3 link = 10^8 / 100Mbps = 10^8 / 10^8 = 1

BW of the R2-R3 link = 10^8 / 1Gbps = 10^8 / 10^9 = 1 (round up)

Therefore OSPF considers the two above links have the same Bandwidth -> R3 will go to 10.1.1.1 via the R1-R3 link. The solution here is to increase the Bandwidth Reference to a higher value using the “auto-cost reference-bandwidth” command under OSPF router mode. For example:

Router(config)#router ospf 1

Router(config-router)#auto-cost reference-bandwidth 10000

This will increase the reference bandwidth to 10000 Mbps which increases the BW of the R2-R3 link to 10^10 / 10^8 = 100.

 

 

QUESTION 128

Refer to the exhibit. For which reason could a BGP-speaking device in autonomous system 65534 be prevented from installing the given route in its BGP table?

 

clip_image014

 

A.

The AS number of the BGP is specified in the given AS_PATH.

B.

The origin of the given route is unknown.

C.

BGP is designed only for publicly routed addresses.

D.

The AS_PATH for the specified prefix exceeds the maximum number of ASs allowed.

E.

BGP does not allow the AS number 65535.

 

Correct Answer: A

Explanation:

BGP is considered to be a ‘Path Vector’ routing protocol rather than a distance vector routing protocol since it utilises a list of AS numbers to describe the path that a packet should take. This list is called the AS_PATH. Loops are prevented because if a BGP speaking router sees it’s own AS in the AS_PATH of a route it rejects the route.

 

 

QUESTION 129

Which statement about the feasibility condition in EIGRP is true?

 

A.

The prefix is reachable via an EIGRP peer that is in the routing domain of the router.

B.

The EIGRP peer that advertises the prefix to the router has multiple paths to the destination.

C.

The EIGRP peer that advertises the prefix to the router is closer to the destination than the router.

D.

The EIGRP peer that advertises the prefix cannot be used as a next hop to reach the destination.

 

Correct Answer: C

Explanation:

The advertised metric from an EIGRP neighbor (peer) to the local router is called Advertised Distance (or reported distance) while the metric from the local router to that network is called Feasible Distance. For example, R1 advertises network 10.10.10.0/24 with a metric of 20 to R2. For R2, this is the advertised distance. R2 calculates the feasible distance by adding the metric from the advertised router (R1) to itself. So in this case the feasible distance to network 10.10.10.0/24 is 20 + 50 = 70.

 

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Before a router can be considered a feasible successor, it must pass the feasibility condition rule. In short, the feasibility condition says that if we learn about a prefix from a neighbor, the advertised distance from that neighbor to the destination must be lower than our feasible distance to that same destination.

Therefore we see the Advertised Distance always smaller than the Feasible Distance to satisfy the feasibility condition.

 

 

QUESTION 130

Which two statements about the function of the stub feature in EIGRP are true? (Choose two.)

 

A.

It stops the stub router from sending queries to peers.

B.

It stops the hub router from sending queries to the stub router.

C.

It stops the stub router from propagating dynamically learned EIGRP prefixes to the hub routers .

D.

It stops the hub router from propagating dynamically learned EIGRP prefixes to the stub routers .

 

Correct Answer: BC

Explanation:

When using the EIGRP Stub Routing feature, you need to configure the distribution and remote routers to use EIGRP, and to configure only the remote router as a stub. Only specified routes are propagated from the remote (stub) router. The router responds to queries for summaries, connected routes, redistributed static routes, external routes, and internal routes with the message “inaccessible.” A router that is configured as a stub will send a special peer information packet to all neighboring routers to report its status as a stub router. Without the stub feature, even after the routes that are sent from the distribution router to the remote router have been filtered or summarized, a problem might occur. If a route is lost somewhere in the corporate network, EIGRP could send a query to the distribution router, which in turn will send a query to the remote router even if routes are being summarized. If there is a problem communicating over the WAN link between the distribution router and the remote router, an EIGRP stuck in active (SIA) condition could occur and cause instability elsewhere in the network. The EIGRP Stub Routing feature allows a network administrator to prevent queries from being sent to the remote router.

Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/eigrpstb.html

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