Download New Updated (July) Cisco 400-101 Actual Test 281-290

Ensurepass

 

 

QUESTION 281

Which three statements about EIGRP and BFD are true? (Choose three.)

 

A.

BFD is independent of the routing protocol, so it can be used as a generic failure detection mechanism for EIGRP.

B.

Some parts of BFD can be distributed to the data plane, so it can be less CPU-intensive than reduced timers, which exist wholly at the control plane.

C.

Reduced EIGRP timers have an absolute minimum detection timer of 1-2 seconds; BFD can provide sub-second failure detection.

D.

BFD is tied to specific routing protocols and can be used for generic fault detection for the OSPF, EIGRP, and BGP routing protocols.

E.

BFD is dependent on the EIGRP routing protocol, so it can be used as a specific
failure detection mechanism.

F.

BFD resides on the control plane, so it is less CPU-intensive than if it resided on the data plane.

 

Correct Answer: ABC

Explanation:

There are several advantages to implementing BFD over reduced timer mechanisms for routing protocols:

 

clip_image002Although reducing the EIGRP, IS-IS, and OSPF timers can result in minimum detection timer of one to two seconds, BFD can provide failure detection in less than one second.

clip_image002[1]Because BFD is not tied to any particular routing protocol, it can be used as a generic and consistent failure detection mechanism for EIGRP, IS-IS, and OSPF.

clip_image002[2]Because some parts of BFD can be distributed to the data plane, it can be less CPU-intensive than the reduced EIGRP, IS-IS, and OSPF timers, which exist wholly at the control plane.

 

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

 

 

QUESTION 282

You are implementing new addressing with EIGRP routing and must use secondary addresses, which are missing from the routing table. Which action is the most efficient solution to the problem?

 

A.

Disable split-horizon on the interfaces with secondary addresses.

B.

Disable split-horizon inside the EIGRP process on the router with the secondary interface addresses.

C.

Add additional router interfaces and move the secondary addresses to the new interfaces.

D.

Use a different routing protocol and redistribute the routes between EIGRP and the new protocol.

 

Correct Answer: A

Explanation:

Normally, routers that are connected to broadcast-type IP networks and that use distance-vector routing protocols employ the split horizon mechanism to reduce the possibility of routing loops. Split horizon blocks information about routes from being advertised by a router out of any interface from which that information originated. This behavior us
ually optimizes communications among multiple routers, particularly when links are broken. However, with nonbroadcast networks, situations can arise for which this behavior is less than ideal. For these situations, you might want to disable split horizon with EIGRP and RIP.

If an interface is configured with secondary IP addresses and split horizon is enabled, updates might not be sourced by every secondary address. One routing update is sourced per network number unless split horizon is disabled.

Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/fipr_c/1cfrip.html

 

 

QUESTION 283

Refer to the exhibit. Which two options are possible states for the interface configured with the given OSPFv3 authentication? (Choose two.)

 

clip_image004

 

A.

GOING UP

B.

DOWN

C.

UNCONFIGURED

D.

GOING DOWN

 

Correct Answer: AB

Explanation:

To configure IPsec, you configure a security policy, which is a combination of the security policy index (SPI) and the key (the key is used to create and validate the hash value). IPsec for OSPFv3 can be configured on an interface or on an OSPFv3 area. For higher security, you should configure a different policy on each interface configured with IPsec. If you configure IPsec for an OSPFv3 area, the policy is applied to all of the interfaces in that area, except for the interfaces that have IPsec configured directly. Once IPsec is configured for OSPFv3, IPsec is invisible to you. The secure socket API is used by applications to secure traffic. The API needs to allow the application to open, listen, and close secure sockets. The binding between the application and the secure socket layer also allows the secure socket layer to inform the application of changes to the socket, such as connection open and close events. The secure socket API is able to identify the socket; that is, it can identify the local and remote addresses, masks, ports, and protocol that carry the traffic requiring security.

Each interface has a secure socket state, which can be one of the following:

OSPFv3 will not send or accept packets while in the DOWN state.

Referene: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/15-sy/iro- 15-sy-book/ip6-route-ospfv3-auth-ipsec.html

 

 

QUESTION 284

Refer to the exhibit. The device with this configuration is unable to reach network 172.31.31.0/24. The next hop router has been verified to have full connectivity to the network. Which two actions can you take to establish connectivity to the network? (Choose two.)

 

clip_image006

 

A.

Create a static route to 172.16.199.0 using the address of the next hop router.

B.

Create a default route to the link address of the next hop router.

C.

Create a static route to the loopback address of the next hop router.

D.

Create a default route to 172.16.199.9.

E.

Modify the existing static route so that the next hop is 0.0.0.0.

F.

Replace the ip default-network command with the ip default-gateway command.

 

Correct Answer: AB

Explanation:

Unlike the ip default-gateway command, you can use ip default-network when ip routing is enabled on the Cisco router. When you configure ip default-network the router considers routes to that network for installation as the gateway of last resort on the router.

 

For every network configured with ip default-network, if a router has a route to that network, that route is flagged as a candidate default route. However, in this case if the router does not a route to the drfault network of 172.16.199.9, then you would need to ensure that this route exisits by creating a static route to 172.16.199.0 using the address of the next hop router, or simply create a default route using the address of the next hop router.

 

 

QUESTION 285

Which algorithm heavily influenced the algorithm used by path-vector protocols?

 

A.

Bellman-Ford

B.

SPF

C.

DUAL

D.

Spanning-Tree

E.

Adaptive

F.

Deflection

 

Correct Answer: A

Explanation:

A path vector protocol is a computer network routing protocol which maintains the path information that gets updated dynamically. Updates which have looped through the network and returned to the same node are easily detected and discarded. This algorithm is sometimes used in Bellman-Ford routing algorithms to avoid “Count to Infinity” problems.

Reference: http://en.wikipedia.org/wiki/Path_vector_protocol

 

 

QUESTION 286

Refer to the exhibit. All of the routers on this network are running RIP. If you edit the R3 RIP process configuration to reduce the number of hops from R3 to R1, which statement about the configuration change is true?

 

clip_image008

 

A.

Configuring no passive-interface for GigabitEthernet0/0 in the R3 RIP process reduces the number of hops to R1 by 2.

B.

Configuring no passive-interface for GigabitEthernet0/0 in the R3 RIP process reduces the number of hops to R1 by 1.

C.

Configuring no passive-interface for GigabitEthernet0/1 in the R3 RIP process reduces the number of hops to R1 by 3.

D.

Configuring no passive-interface for GigabitEthernet0/1 in the R3 RIP process reduces the number of hops to R1 by 1.

 

Correct Answer: A

Explanation:

By changing the link from R3 to R2 to not be passive, traffic can then take the direct route from R3-R2-R1 instead of the longer path of R3-R6-R5-R4-R1, resulting in two less hops.

 

 

QUESTION 287

Where should the passive-interface command be used?

 

A.

Under the routing process for interfaces that need to be routed, but prevented from peering

B.

under the routing process for interfaces that need to be routed and allowed to peer

C.

under the interface configuration for interfaces that need to be routed, but prevented from peering

D.

under the interface configuration for interfaces that need to be routed and allowed to peer

E.

under the VTY configuration within global configuration mode

 

Correct Answer: A

Explanation:

Passive-interface is a feature you enable on a per interface basis which allows a particular interface to participate in a routing process but prevents that interface from forming neighbor relationships by not sending hello packets and discarding received hello packets.

 

 

QUESTION 288

Refer to the exhibit. Which statement about the device routing table is true?

 

clip_image010

 

A.

Only networks 10.10.10.0/24 and smaller from host 192.168.168.1 are in the routing table.

B.

Only networks 10.10.10.0/24 and larger from host 192.168.168.1 are in the routing table.

C.

Only network 10.10.10.0/24 from host 192.168.168.1 is in the routing table.

D.

Networks 10.10.10.0/24 and smaller from any host are in the routing table.

 

Correct Answer: A

Explanation:

When you add the keywords “GE” and “LE” to the prefix-list, the “len” value changes its meaning. When using GE and LE, the len value specifies how many bits of the prefix you are checking, starting with the most significant bit.

ip prefix-list LIST permit 1.2.3.0/24 le 32

This means:Check the first 24 bits of the prefix 1.2.3.0The subnet mask must be less than or equal to 32

Reference: http://blog.ine.com/2007/12/26/how-do-prefix-lists-work/

 

 

QUESTION 289

Refer to the exhibit. R1 is performing mutual redistribution, but OSPF routes from R3 are unable to reach R2. Which three options are possible reasons for this behavior? (Choose three.)

 

clip_image012

A.

R1 requires a seed metric to redistribute RIP.

B.

The RIP version supports only classful subnet masks.

C.

R1 is filtering OSPF routes when redistributing into RIP.

D.

R3 and R1 have the same router ID.

E.

R1 and R3 have an MTU mismatch.

F.

R2 is configured to offset OSPF routes with a metric of 16.

 

Correct Answer: ACF

Explanation:

A. RIP requires a seed metric to be specified when redistributing routes into that protocol. A seed metric is a “starter metric” that gives the RIP process a metric it can work with. The OSPF metric of cost is incomprehensible to RIP, since RIP’s sole metric is hop count. We’ve got to give RIP a metric it understands when redistributing routes into that protocol, so let’s go back to R1 and do so.

C. Filtering routes is another explanation, if the routes to R2 are boing filtered from being advertised to R1.

F. If the metric is offset to 16, then the routes will have reached the maximum hop count when redistributed to RIP. The max hop count for RIP is 16.

 

 

QUESTION 290

Refer to the exhibit. If the downstream router has a summary route configured, which two actions must you take on the local router to create the summary route that summarizes all routes from the downstream router? (Choose two.)

 

clip_image014

 

A.

Configure the summary address on the interface.

B.

Use 10.0.0.0 255.248.0.0 as the summary route.

C.

Configure the summary address in the EIGRP process.

D.

Use 10.0.0.0 255.252.0.0 as the summary route.

E.

Configure a route map to permit the route.

F.

Configure a distribute list in.

 

Correct Answer: AB

Explanation:

Route summarization works in conjunction with the ip summary-address eigrp interface configuration command, in which additional summarization can be performed To correctly summarize all the networks shown, the correct route to use is 10.0.0.0 255.248.0.0.

Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/fipr_c/1cfeigrp.html

 

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