Download New Updated (July) Cisco 400-101 Actual Test 291-300

Ensurepass

 

QUESTION 291

Which three statements about RIP timers are true? (Choose three.)

 

A.

The default update timer is 30 seconds.

B.

The default invalid timer is 180 seconds.

C.

The default holddown timer is 180 seconds.

D.

The default flush timer is 60 seconds.

E.

The default scan timer is 60 seconds.

F.

The default hello timer is 5 seconds.

 

Correct Answer: ABC

Explanation:

The routing information protocol uses the following timers as part of its operation:

Update Timer

The update timer controls the interval between two gratuitous Response Message. By default the value is 30 seconds. The response message is broadcast to all its RIP enabled interface.

Invalid Timer

The invalid timer specifies how long a routing entry can be in the routing table without being updated. This is also called as expiration Timer. By default, the value is 180 seconds. After the timer expires the hop count of the routing entry will be set to 16, marking the destination as unreachable.

Flush Timer

The flush timer controls the time between the route is invalidated or marked as unreachable and removal of entry from the routing table. By default the value is 240 seconds. This is 60 seconds longer than Invalid timer. So for 60 seconds the router will be advertising about this unreachable route to all its neighbors. This timer must be set to a higher value than the invalid timer.

Hold-down Timer

The hold-down timer is started per route entry, when the hop count is changing from lower value to higher value. This allows the route to get stabilized. During this time no update can be done to that routing entry. This is not part of the RFC 1058. This is Cisco’s implementation. The default value of this timer is 180 seconds.

Reference: http://en.wikipedia.org/wiki/Routing_Information_Protocol#Timers

 

 

QUESTION 292

Which timer expiration can lead to an EIGRP route becoming stuck in active?

 

A.

hello

B.

active

C.

query

D.

hold

 

Correct Answer: B

Explanation:

As noted above, when a route goes into the active state, the router queries its neighbors to find a path to the pertinent network. At this point, the router starts a three minute active timer by which time it must receive replies from all queried neighbors. If a neighbor has feasible successors for the route, it will recalculate its own local distance to the network and report this back. However, if a neighbor does not have a feasible successor, it also goes into active state. In some cases, multiple routers along multiple query paths will go into active state as routers continue to query for the desired route. In most cases, this process will yield responses from all queried routers and the sought after route will transition back into the passive state within the three minute SIA query timer. In the case that none of the queried routers can provide a feasible successor, the route is cleared.

In some cases, a response is not received between two neighbor routers because of link failures, congestion or some other adverse condition in either the network or on the queried router, and the three minute active timer expires on the router originating the query. When this happens, the querying router that did not receive a response logs a “DUAL-3-SIA” or “stuck-in-active” error for the route and then drops and restarts its adjacency with the non-responding router.

Reference: http://www.packetdesign.com/resources/technical-briefs/diagnosing-eigrp-stuck-active

 

 

QUESTION 293

Which three values can be used to tag external EIGRP routes? (Choose three.)

 

A.

< span lang="EN-US" style="font-family: ; mso-font-kerning: 0pt; mso-no-proof: yes">The router ID of the router that redistributed the route

B.

The administrative distance of the external protocol

C.

The protocol ID of the external protocol

D.

The cost to reach the router that redistributed the route

E.

The metric from the external protocol

F.

The router ID of the router from which the external protocol route was learned

 

Correct Answer: ACE

Explanation:

EIGRP has the notion of internal and external routes. Internal routes are ones that have been originated within an EIGRP autonomous system (AS). Therefore, a directly attached network that is configured to run EIGRP is considered an internal route and is propagated with this information throughout the EIGRP AS. External routes are ones that have been learned by another routing protocol or reside in the routing table as static routes. These routes are tagged individually with the identity of their origination.

External routes are tagged with the following information:

Reference: http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/13669-1.html#route_tagging

 

 

QUESTION 294

Which data plane protocol does EIGRP Over the Top use?

 

A.

MPLS

B.

GRE

C.

LISP

D.

IP-in-IP

 

Correct Answer: C

Explanation:

The EIGRP Over the Top solution can be used to ensure connectivity between disparate Enhanced Interior Gateway Routing Protocol (EIGRP) sites. This feature uses EIGRP on the control plane and Locator ID Separation Protocol (LISP) encapsulation on the data plane to route traffic across the underlying WAN architecture. EIGRP is used to distribute routes between customer edge (CE) devices within the network, and the traffic forwarded across the WAN architecture is LISP encapsulated. Therefore, to connect disparate EIGRP sites, you must configure the neighbor command with LISP encapsulation on every CE in the network.

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/xe-3s/ire-xe-3s-book/ire-eigrp-over-the-top.html

 

 

 

 

QUESTION 295

Which statement about the feasible distance in EIGRP is true?

 

A.

It is the maximum metric that should feasibly be considered for installation in the RIB.

B.

It is the minimum metric to reach the destination as stored in the topology table.

C.

It is the metric that is supplied by the best next hop toward the destination.

D.

It is the maximum metric possible based on the maximum hop count that is allowed.

 

Correct Answer: B

Explanation:

An EIGRP router advertises each destination it can reach as a route with an attached metric. This metric is called the route’s reported distance (the term advertised distance has also been used in older documentation). A successor route for any given destination is chosen as having the lowest computed feasible distance; that is, the lowest sum of reported distance plus the cost to get to the advertising router.

By default, an EIGRP router will store only the route with the best (lowest

) feasible distance in the routing table (or, multiple routes with equivalent feasible distances).

Reference: http://packetlife.net/blog/2010/aug/9/eigrp-feasible-successor-routes/

 

 

QUESTION 296

Which statement about the EIGRP RTO is true?

 

A.

It is six times the SRTT.

B.

It is the time that it normally takes for an update to be received by a peer.

C.

It is the time that it normally takes to receive a reply to a query.

D.

It is the average time that it takes for a reliable packet to be acknowledged.

 

Correct Answer: A

Explanation:

The RTO is typically six times the SRTT, the value may vary from a minimum of 200 microseconds (ms) to a maximum of 5 seconds (s).

Reference: EIGRP for IP: Basic Operation and Con

figuration, Alvaro Retana, Russ White, Don Slice – 2000

 

 

QUESTION 297

Which option describes the purpose of the leak-map keyword in the command eigrp stub connected leak-map EigrpLeak?

 

A.

It allows the specified static routes to be advertised.

B.

It allows exceptions to the route summarization that is configured.

C.

It allows specified EIGRP-learned routes to be advertised.

D.

It restricts specified connected routes from being advertised.

 

Correct Answer: C

Explanation:

Example: eigrp stub leak-map Command

In the following example, the eigrp stub command is issued with the leak-map name keyword- argument pair to configure the device to reference a leak map that identifies routes to be advertised that would have been suppressed otherwise.

Device(config)# router eigrp 1

Device(config-router)# network 10.0.0.0

Device(config-router)# eigrp stub leak-map map1

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/15-mt/ire-15-mt-book/ire-eigrp-stub-rtg.html#GUID-FB899CA9-E9DE-48D8-8048-C971179E4E24

 

 

QUESTION 298

Refer to the exhibit. If OSPF is implemented on the network, which additional configuration is needed to allow traffic from host 10.4.1.15/24 to host 10.1.2.20/24?

 

clip_image002

 

A.

A virtual link between router 2 and router 4

B.

A virtual link between router 3 and router 4

C.

A virtual link between router 2 and router 3

D.

The current design allows traffic between the two hosts.

 

Correct Answer: D

Explanation:

This specific traffic from 10.4.1.0/24 to 10.1.2.0/24 would work because this traffic crosses only over the single OSPF area of 0.0.0.1.

However, traffic from hosts on R4 to R1 would indeed need a virtual link, since area 0.0.0.2 is not connected to the backbone area of 0.0.0.0.

 

 

 

 

 

 

 

 

 

 

 

QUESTION 299

Refer to the exhibit. Which OSPFv3 routes will be visible in the routing table of R2?

 

clip_image004

 

A.

< p class="MsoNormal" style="margin: 0cm 0cm 0pt; text-autospace: ; mso-layout-grid-align: none" align="left">2001:12::1/128

B.

2001:12::1/128, 2001:112::1/128

C.

2001:12::2/128

D.

No OSPFv3 routes will be visible.

 

Correct Answer: D

Explanation:

The command “ipv6 unicast-routing” needs to be configured on both routers before any IPv6 routes will be seen.

 

 

QUESTION 300

Which option describes how a router responds if LSA throttling is configured and it receives the identical LSA before the interval is set?

 

A.

The LSA is added to the OSPF database and a notification is sent to the sending router to slow down its LSA packet updates.

B.

The LSA is added to the OSPF database.

C.

The LSA is ignored.

D.

The LSA is ignored and a notification is sent to the sending router to slow down its LSA packet updates.

 

Correct Answer: C

Explanation:

How OSPF LSA Throttling Works

The timers throttle lsa all command controls the generation (sending) of LSAs. The first LSA is always generated immediately upon an OSPF topology change, and the next LSA generated is controlled by the minimum start interval. The subsequent LSAs generated for the same LSA are rate-limited until the maximum interval is reached. The “same LSA” is defined as an LSA instance that contains the same LSA ID number, LSA type, and advertising router ID. The timers lsa arrival command controls the minimum interval for accepting the same LSA. If an instance of the same LSA arrives sooner than the interval that is set, the LSA is dropped. It is recommended that the arrival interval be less than or equal to the hold-time interval of the timers throttle lsa all command.

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

 

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