[Free] Download New Latest (November) Cisco 400-201 Actual Tests 121-130

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QUESTION 121

How do routers in an IS-IS Level-1 domain exit to reach other Level-1 domains? (Choose two.)

 

A.

Level-1 routers use default routes announced by Level-2 routers in Level-1 domain

B.

Level-1 routers use default routes installed based on ATT bit (Attach Bit) in announcements from Level-1-2 router

C.

Level-1 routers use specific routes, for other Level-1 domain, announced by Level-1-2 router by route leaking feature of Cisco IOS

D.

Level-1 routers use specific routes, for other Level-1 domain, announced by Level-2 router by route-leaking feature of Cisco IOS

 

Correct Answer: BC

 

 

QUESTION 122

Which two statements are true about SAFI & AFI?

 

A.

Subsequent Address Family identifier (SAFI) provides additional information about the type of the Network Layer ports carried in the BGP update.

B.

Address Family identifier (AFI) field carries the identity of the Network Layer ports for which the BGP speaker intends to advertise multiple paths.

C.

Subsequent Address Family identifier (SAFI) provides additional information about the type of the Network Layer Reachability Information carried in the attribute.

D.

Address Family identifier (AFI) carries the identity of the Network Layer protocol for which the BGP speaker intends to advertise multiple paths.

 

Correct Answer: CD

 

 

QUESTION 123

Which two m
odels are the models of DiffServ-Aware Traffic Engineering? (Choose two)

 

A.

Policy-based Model

B.

Class based Model

C.

Russian Doll Model

D.

Global Tunnel Model

E.

Maximum Allocation Model

 

Correct Answer: CE

Explanation:

Therefore in practice, a Network Administrator might prefer to use:

the Maximum Allocation Model when s/he needs to ensure isolation across all Class Types without having to use pre-emption, and s/he can afford to risk some QoS degradation of Class Types other than the Premium Class.

the Russian Dolls Model when s/he needs to prevent QoS degradation of all Class Types and can impose preemption.

 

 

QUESTION 124

Which methods would enable traffic to be forwarded along an MPLS TE tunnel (Choose four.)

 

A.

MP-BGP routing

B.

Static routing

C.

Policy routing

D.

Autoroute

E.

Forwarding adjacency

 

Correct Answer: BCDE

 

 

QUESTION 125

Which of the following are steps to configure destination-based Remote Triggered Black Hole (RTBH) filtering? (Choose three.)

 

A.

Configure BGP between trigger and black hole routers.

B.

Configure OSPF between trigger router and black hole routes

C.

Configure all edge routers with static (reserved) host route to Null0

D.

Configure on trigger router to advertise victim host route with community

E.

Activate black hole by redistributing route for victim into BGP with next-hop set to the static (reserved) hostroute configured on edge routers.

 

Correct Answer: ACE

Explanation:

The three steps in destination-based black hole filtering are summarized below.

Step 1. The setup (preparation)

A trigger is a special device that is installed at the NOC exclusively for the purpose of triggering a black hole.

The trigger must have an iBGP peering relationship with all the edge routers, or, if using route reflectors, it must have an iBGP relationship with the route reflectors in every cluster. The trigger is also configured to redistribute static routes to its iBGP peers. It sends the static route by means of an iBGP routing update.

 

Step 2. The trigger

An administrator adds a static route to the trigger, which redistributes the route by sending a BGP update to all its iBGP peers, setting the next hop to the target destination address under attack as 192.0.2.1 in the current example. The PEs receive their iBGP update and set their next hop to the target to the unused IP address space 192.0.2.1. The route to this address is set to null0 in the PE, using a static routing entry in the router configuration. The next hop entry in the forwarding information base (FIB) for the destination IP (target) is now updated to null0. All traffic to the target will now be forwarded to Null0 at the edge and dropped.

 

Step 3. The withdrawal

Once the trigger is in place, all traffic to the target destination is dropped at the PEs. When the threat no longer exists, the administrator must manually remove the static route from the trigger, which sends a BGP route withdrawal to its iBGP peers. This prompts the edge routers to remove the existing route for the target that ispointed to 192.0.2.1 and to install a new route based on the IGP routing information base (RIB).

 

 

QUESTION 126

Select the two answers that best describe the IP Event Dampening feature.

 

A.

The IP Event Dampening uses exponential decay mechanism to suppress the effects of excessive interface flapping.

B.

BGP Operators use IP Event Dampening to suppress the effect of unstable internet Routes.

C.

The IP Event Dampening works with routing protocols by stopping the announcement of dampened Interface subnets in their updates.

D.

When IP Event Dampened internet routes reach their re-use limit, BGP installs them in the Routing Table and announces them to other BGP speakers.

 

Correct Answer: AC

Explanation:

1.10. High Availability

 

 

QUESTION 127

The Attribute field within the IS-IS LSP header contains which of the following flags? (Choose four)

 

A.

IS-Type

B.

Overload (LSPDBOL)

C.

Pseudonode (PN)

D.

Attached (ATT)

E.

Fragment (Frag-Nr)

F.

Partition (P)

 

Correct Answer: ABDF

Explanation:

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Partition Repair (P): Although this bit exists in both L1 and L2 LSPs, it is relevant only in L2 LSPs. When this bit is set to 1, it indicates that the originating router supports the automatic repair of area partitions. Cisco IOS does not support this feature; it always originates LSPs with the P bit set to 0.

 

Attachment (ATT): A 4-bit field indicating whether the originating router is attached to one or more areas.

 

Although this bit exists in both L1 and L2 LSPs, it is relevant only in L1 LSPs originated by L1/L2 routers to indicate that it is also a L2 router, which is a potential exit to reach other areas. Reading from left to right (bits 7 – 4), the bits indicate the Error metric, the Expense metric, the Delay metric, and the Default metric. Cisco IOSsupports only the default metric, so bits 5 – 7 are always 0.

 

Overload (OL): The Link-State Database Overload bit. This bit is often set to 0. A router set this bit on its LSPs when unable to store the entire LSDB. Routers receiving an LSP with the OL bit set will not use the originating router as a transit router as its routing table is incomplete, which may result in suboptimal routing and even routing loops; but they will still forward packets destined to the directly connected networks or interfaces of the originating router.

IS Type A 2-bit field indicating whether the originating router is an L1 or L2 IS.

01 – L1; 11 – L2; 00 and 10 are unused values.

An L1/L2 router sets the bits accordingly upon its L1 and L2 LSPs.

 

 

 

 

 

QUESTION 128

What three major tasks are performed by a Designated Intermediate System in an ISIS pseudonode environment? (Choose three.)

 

A.

updating the pseudonode LSP

B.

maintaining pseudonode link-state information

C.

creating the pseudonode LSP

D.

flooding LSPs over the LAN

E.

election of the pseudonode

 

Correct Answer:
ACD

Explanation:

Two major tasks are performed by the DIS:

Creating and updating pseudonode LSP for reporting links to all systems on the broadcast subnetwork. See the Pseudenode LSP section for more information.

Flooding LSPs over the LAN.

Flooding over the LAN means that the DIS sends periodic complete sequence number protocol data units (CSNPs) (default setting of 10 seconds) summarizing the following information:

LSP ID

Sequence Number

Checksum

Remaining Lifetime

 

The DIS is responsible for flooding. It creates and floods a new pseudonode LSP for each routing level in which it is participating (Level 1 or Level 2) and for each LAN to which it is connected. A router can be the DIS for all connected LANs or a subset of connected LANs, depending on the IS-IS priority or the Layer 2 address.

 

The DIS will also create and flood a new pseudonode LSP when a neighbor adjacency is established, torn down, or the refresh interval timer expires. The DIS mechanism reduces the amount of flooding on LANs.

 

 

QUESTION 129

In which of the following BGP-related events is an End-of-RIB (EOR) message sent? (Choose two.)

 

A.

Following a link flap in the BGP speaker’s AS

B.

During initial convergence.

C.

Following a Route Processor Switchover.

D.

Just before sending a CEASE message to tear down the session.

E.

During capability negotiation

 

Correct Answer: BC

Explanation:

The Peer Router must signal the completion of the initial routing update by sending the End-of-RIB marker (discussed below)

While continuing to forward packets, the Peer Router refreshes the Restarting Router with any relevant BGP updates. The Peer Router indicates completion of this process by sending an End-of-RIB (EOR) marker. The EOR marker for IPv4 is a BGP update message that is of the minimum length–23 bytes. The EOR does not contain any routes to be added or withdrawn. Essentially, it is an “empty” update, whose sole purpose is to indicate that all available routes have been sent. The EOR marker helps speed convergence, because it allows the router to begin best-path selection as quickly as possible, without waiting for the timer to expire.

Once the Restarting Router has received all available routes from each peer, it can conduct best-path selection, and send any updates to its Peer Routers. The Restarting Router will also use the EOR to indicate the completion of this process.

 

 

QUESTION 130

Which three statements about MPLS Label Distribution Protocol (LDP) are valid?

 

A.

LDP hello packets are sent to UDP port 646

B.

LDP hello packets are sent to TCP port 711

C.

LDP sessions are TCP sessions to port 646

D.

LDP sessions are TCP sessions to port 711

E.

LDP establishes a peer relationship with another router that must be directly attached.

F.

LDP can establishes a peer relationship with another router that is not directly attached

 

Correct Answer: ACF

 

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