Ensurepass

 

QUESTION 41

How many hash buckets does Cisco Express Forwarding use for load balancing?

 

A.

8

B.

16

C.

24

D.

32

 

Correct Answer: B

Explanation:

In order to understand how the load balance takes place, you must first see how the tables relate. The Cisco Express Forwarding table points to 16 hash buckets (load share table), which point to the adjacency table for parallel paths. Each packet to be switched is broken up into the source and destination address pair and checked against the loadshare table. Reference: http://www.cisco.co
m/c/en/us/support/docs/ip/express-forwarding-cef/18285-loadbal- cef.html

 

 

QUESTION 42

Which three features require Cisco Express Forwarding? (Choose three.)

 

A.

NBAR

B.

AutoQoS

C.

fragmentation

D.

MPLS

E.

UplinkFast

F.

BackboneFast

 

Correct Answer: ABD

Explanation:

QoS Features That Require CEF

 

These class-based QoS features are supported only on routers that run CEF.

 

Network Based Application Recognition (NBAR) provides intelligent network classification. For more information, refer to Network Based Application Recognition.

 

The AutoQoS -VoIP feature simplifies and speeds up the implementation and provisioning of QoS for VoIP traffic. This feature is enabled with the help of the auto qos voip command. CEF must be enabled at the interface or ATM PVC before the auto qos command can be used. For more information about this feature and its prerequisites, refer to AutoQoS – VoIP.

 

From MPLS Fundamentals – Luc De Ghein

Why Is CEF Needed in MPLS Networks?

Concerning MPLS, CEF is special for a certain reason; otherwise, this book would not explicitly cover it. Labeled packets that enter the router are switched according to the label forwarding information base (LFIB) on the router. IP packets that enter the router are switched according to the CEF table on the router. Regardless of whether the packet is switched according to the LFIB or the CEF table, the outgoing packet can be a labeled packet or an IP packet

 

Reference: http://www.cisco.com/c/en/us/support/docs/asynchronous-transfer-mode-atm/ip-to-atm-class-of-service/4800-cefreq.html

 

 

QUESTION 43

Which two options are interface requirements for turbo flooding? (Choose two.)

 

A.

The interface is Ethernet.

B.

The interface is configured for ARPA encapsulation.

C.

The interface is PPP.

D.

The interface is configured for GRE encapsulation.

E.

The interface is configured for 802.1Q encapsulation.

 

Correct Answer: AB

Explanation:

In the switch, the majority of packets are forwarded in hardware; most packets do not go through the switch CPU. For those packets that do go to the CPU, you can speed up spanning tree-based UDP flooding by a factor of about four to five times by using turbo-flooding. This feature is supported over Ethernet interfaces configured for ARPA encapsulation.

Reference: http://www.cisco.com/c/en/us/td/docs/switches/metro/me3400/software/release/12-2_50_se/configuration/guide/scg/swiprout.html

 

 

QUESTION 44

Which three option are sub-subfields of the IPv4 Option Type subfield? (Choose three.)

 

A.

Option Class

B.

GET

C.

Copied

D.

PUSH

E.

Option Number

F.

TTL

 

Correct Answer: ACE

Explanation:

Each IP option has its own subfield format, generally structured as shown below. For most options, all three subfields are useD. Option Type, Option Length and Option Data.

 

clip_image002

 

Reference: http://www.tcpipguide.com/free/t_IPDatagramOptionsandOptionFormat.htm

 

 

QUESTION 45

Which TCP mechanism prevents the sender from sending data too quickly for the receiver to process?

 

A.

Congestion control

B.

Error detection

C.

Selective acknowledgement

D.

Flow control

 

Correct Answer: D

Explanation:

In data communications, flow control is the process of managing the rate of data transmission between two nodes to prevent a fast sender from overwhelming a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed with data from transmitting node.

Reference: http://en.wikipedia.org/wiki/Flow_control_(data)

 

 

QUESTION 46

Which two packet types does an RTP session consist of? (Choose two.)

 

A.

TCP

B.

RTCP

C.

RTP

D.

ICMP

E.

BOOTP

F.

ARP

 

Correct Answer: BC

Explanation:

An RTP session is established for each multimedia stream. A session consists of an IP address with a pair of ports for RTP and RTCP. For example, audio and video streams use separate RTP sessions, enabling a receiver to deselect a particular stream. The ports which form a session are negotiated using other protocols such as RTSP (using SDP in the setup method) and SIP. According to the specification, an RTP port should be even and the RTCP port is the next higher odd port number.

Reference: http://en.wikipedia.org/wiki/Real-time_Transport_Protocol

 

 

QUESTION 47

Which technology can create a filter for an embedded packet capture?

 

A.

Control plane policing

B.

Access lists

C.

NBAR

D.

Traffic shaping

 

Correct Answer: B

Explanation:

A filter can be applied to limit the capture to desired traffic. Define an Access Control List (ACL) within config mode and apply the filter to the buffer:

 

ip access-list extended BUF-FILTER

permit ip host 192.168.1.1 host 172.16.1.1

permit ip host 172.16.1.1 host 192.168.1.1

monitor capture buffer BUF filter access-list BUF-FILTER

 

Reference: http://www.cisco.com/c/en/us/support/docs/ios-nx-os-software/ios-embedded-packet-capture/116045-productconfig-epc-00.html

 

 

QUESTION 48

Which option describes a limitation of Embedded Packet Capture?

 

A.

It can capture data only on physical interfaces and subinterfaces.

B.

It can store only packet data.

C.

It can capture multicast packets only on ingress.

D.

It can capture multicast packets only on egress.

 

Correct Answer: C

Explanation:

Restrictions for Embedded Packet Capture

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/epc/configuration/15-mt/epc-15-mt-book/nm-packet-capture.html

 

 

QUESTION 49

Refer to the exhibit. A Cisco Catalyst 6500 Series Switch experiences high CPU utilization. What can be the cause of this issue, and how can it be prevented?

 

clip_image004

 

A.

The hardware routing table is full. Redistribute from BGP into IGP.

B.

The software routing table is full. Redistribute from BGP into IGP.

C.

The hardware routing table is full. Reduce the number of routes in the routing table.

D.

The software routing table is full. Reduce the number of routes in the routing table.

 

Correct Answer: C

Explanation:

FIB TCAM Exception – If you try to install more routes than are possible into the FIB TCAM you will see the following error message in the logs:

 

CFIB-SP-STBY-7-CFIB_EXCEPTION : FIB TCAM exception, Some entries will be software switched

 

%CFIB-SP-7-CFIB_EXCEPTION : FIB TCAM exception, Some entries will be software switched %CFIB-SP-STBY-7-CFIB_EXCEPTION : FIB TCAM exception, Some entries will be software switched

 

This error message is received when the amount of available space in the TCAM is exceeded. This results in high CPU. This is a FIB TCAM limitation. Once TCAM is full, a flag will be set and FIB TCAM exception is received. This stops from adding new routes to the TCAM.
Therefore, everything will be software switched. The removal of routes does not help resume hardware switching. Once the TCAM enters the exception state, the system must be reloaded to get out of that state. You can view if you have hit a FIB TCAM exception with the following command:

 

6500-2#sh mls cef exception status

Current IPv4 FIB exception state = TRUE

Current IPv6 FIB exception state = FALSE

Current MPLS FIB exception state = FALSE

 

When the exception state is TRUE, the FIB TCAM has hit an exception. The maximum routes that can be installed in TCAM is increased by the mls cef maximum-routes command.

Reference: https://supportforums.cisco.com/document/59926/troubleshooting-high-cpu-6500-sup720

 

 

QUESTION 50

Refer to the exhibit. Your network is suffering excessive output drops. Which two actions can you take to resolve the problem? (Choose two.)

 

clip_image006

A.

Install a switch with larger buffers.

B.

Configure a different queue set.

C.

Reconfigure the switch buffers.

D.

Configure the server application to use TCP.

E.

Update the server operating system.

 

Correct Answer: AB

Explanation:

Installing a switch with larger buffers and correctly configuring the buffers can solve output queue problems.

For each queue we need to configure the assigned buffers. The buffer is like the `storage’ space for the interface and we have to divide it among the different queues. This is how to do it:

mls qos queue-set output <queue set> buffers Q1 Q2 Q3 Q4

In this example, there is nothing hitting queue 2 or queue 3 so they are not being utilized.

 

Free VCE & PDF File for Cisco 400-101 Real Exam

Instant Access to Free VCE Files: CCNA | CCNP | CCIE …
Instant Access to Free PDF Files: CCNA | CCNP | CCIE …

Comments are closed.