CCNP-BCMSN考前热身之二

26,Unlike IGMP version 1, in which the DR and the IGMP querier are typically the same router, in IGMP version 2, the two functions are separated. The DR and the IGMP querier are selected based on different criteria and may be different routers on the same subnet. The DR is the router with the highest IP address on the subnet, whereas the IGMP querier is the router with the lowest IP address.

 

27,A querier election across switches is based either on IP address or MAC address. For an inbound query, if the source IP address is nonzero, the election is based on the IP address, and the switch with the lower source IP address becomes the querier. If the source IP address is zero for an inbound query, then the election is based on the source MAC address, and the switch with the lower MAC address wins the election and becomes the querier. The switch that becomes the nonquerier maintains an “other querier interval” timer. When this timer expires, the switch elects itself as the querier

 

28,To configure TK1 for PIM, first you enable IP multicast routing:

TK1# ip multicast-routing

Then you enable PIM on the interface

TK1#interface type number

TK1#ip pim sparse-dense-mode

 

29,Fast switching allows higher throughput by switching a packet using a cache created by the initial packet sent to a particular destination. Destination addresses are stored in the high-speed cache to expedite forwarding. Routers offer better packet-transfer performance when fast switching is enabled. Fast switching is enabled by default on all interfaces that support fast switching. Fast switching of IP multicast packets is inabled by default on all interface, with one exception:it is disabled and not supported over X.25 encapsulated interfaces.

 

30,IGMP snooping manages multicast traffic at layer 2 by configuring layer 2 LAN interfaces dynamically to forward multicast traffic only to those interfaces that want to receive it

 

31,CGMP is not enabled by default. It must be manually enabled. Furthermore, you cannot enable CGMP on a switch if IGMP snooping is already enabled on that switch

 

32,Cisco Group Management Protocol(CGMP) is a cisco proprietary protocol which enables IP multicasting at layer 2 on cisco’s Catalyst switches that do not distinguish between IP multicast data packets and IGMP Report messages, which are both MAC level addressed to the same group address

PIM( Protocol-independent Multicast) handles the transmission of multicast packets to all hosts in the multicast group while preventing loops and wasted bandwidth. The two main PIM modes are sparse and dense. PIM is fundamentally used with routers

Routers use the Internet Group Management protocol(IGMP) to learn whether members of a group are present on directly attached subnets, and whether or not to forward multicast packets onto those networks. Hosts join multicast groups by sending IGMP report messages.

 

33,You want to configure CGMP on switch TK1, which of the following statements is correct for configuring cisco group management protocol on this switch?

PIM must be configured on the CGMP router

Protocol Independent Multicast(PIM) is one of the required elements for multicast configuration. It enables IGMP on the router and allows it to receive and forward traffic on the specified interface. PIM must be enabled on every interface that is to participate in the multicast network

 

34,The testking network is migrating from IGMP version 1 to IGMP version 2. what message type was added in IGMPv2?

Leave report

A new IGMP type was created for the IGMPv2 leave group message. Explicit leave messages were not available in IGMP version 2

IGMPv2一个显著的特点就是有离开进程，这样就不用考虑超时.

 

35, IGMP侦听是一种多播控制机制，它通过查看二层和三层的IP多播信息维护第2层多播转发表，在三层交换机上，很容易实现（查看上面的原理），而在二层交换机上，无法区分IGMP数据包和常规的多播数据，所以在运行IGMP的交换机必须查看每个多播数据包，来确认是否包含IGMP相关信息。所以在低端交换机上，实现IGMP监听，会严重影响性能。所以当使用IGMP监听IGMP包，流量过重时就能会降低性能

 

36,You want to disable CGMP on switch TK1.which command would you enter if you had to disable CGMP on a non-IOS command-based switch?

Set cgmp disable

 

37,Dense mode routing protocols include the following:

Distance Vetor Multicast Routing Protocol(DVMRP)

Multicast Open Shortest Path First(MOSPF)

Protocol-Independent Multicast Dense Mode(PIM DM)

 

38,Jitter is causing problems with the VOIP application in the TestKing network. What causes network jitter?

a. Variable queue delays

b. Packet drops

c. Transmitting too many small packets

d. compression

delay variation or jitter is the difference in the delay times of consecutive packets. A jitter buffer is often used to smooth out arrival times, but there are instantaneous and total limits on buffering ability. Any type of buffering used to reduce jitter directly increases total network delay. In general, traffic requiring low latency also requires a minimum variation in latency

63,VOIP is being implemented on the TestKing network. In a properly designed network, what is the maximum amount of time a voice package should spend crossing a network?

150 milliseconds

 

39,Loss, jitter, and delay are the three reasons for implementing QoS features on modern networks. Loss is when a packet disappears on a network. Jitter is a timing mismatch between two way traffic, and delay is when a packet takes too long to get somewhere

 

40,Which QoS mechanisms can you use on a converged network to improve VoIP quality?

a. the use of a queuing method that will give VoIP traffic strict priority over other traffic

b. the use of RTP header compression for the VoIP traffic

c. the proper classification and marking of the traffic as close to the source as possible

 

41,By creating a robust foundation of basic connectivity and protocol implementation, Cisco AVVID network infrastructure addresses five primary concerns of network deployment:

High availability

Quality of service(QoS)

Security

Mobility and scalability

 

42,Cisco IOS QoS includes the following features that provide controlled load service, which is a kind of integrated service:

Resource reservation protocol(RSVP) can be used by applications to signal their QoS requirements to the router

Intelligent queuing mechanisms can be used with RSVP to provide the following kinds of services:

Guaranteed rate service, which allows applications to reserve bandwidth to meet their requirements. For example, a Voice over IP(VoIP) application can reserve 32 Mbps end to end using this kind of service. Cisco IOS QoS uses weighted fair queuing(WFQ) with RSVP to provide this kind of service

 Controlled load service, which allows applications to have low delay and high throughput even during times of congestion. For example, adaptive real-time applications such as playback of a recorded conference can use this kind of service. Cisco IOS QoS uses RSVP with Weighted Random Early Detection(WRED) to provide this kind of service

 

43,WFQ stands for weighted fair queuing. WFQ is one of Cisco’s premier queuing techniques. It is a flow-based queuing algorithm that does two things simultaneously: it schedules interactive traffic to the front of the queue to reduce response time, and it fairly shares the remaining bandwidth between high bandwidth flows. By doing this, it can ensure fair treatment for all traffic types, while ensuring that small transmissions are serviced in a timely manner, rather than waiting for a long data transfer to finish

 

44,RED and WRED are congestion avoidance mechanisms. RED is a congestion avoidance mechanism that takes advantage of TCP’s congestion control mechanism. WRED generally drops packets selectively based on IP precedence. Packets with a higher IP precedence are less likely to be dropped than packets with a lower precedence. WRED is a derivative of RED that also uses TCP’s congestion control mechanism

 

45,What is true about a SPAN session?

a.affects switching traffic on source ports

b. associates multiple source interfaces with a single destination interface

c. eliminates multiple copies of packets

d. associates a source interface with multiple destination interfaces

answer:b

 

46,You are a professor at the TestKing academy, and a student asks you to describe’ netflow traffic flow’ to her. How would you respond?

It is a uni-directional sequence of packets between a particular source and destination

 

47,You are a CCNP and are configuring a switching solution with a set based(non IOS) switch. Which command would you enter to disable SPAN?

Answer:set span disable

 

48,Switch TK1 has IP accounting enabled. Which command would you enter if you wanted to define filters to control the hosts for which IP accounting information is kept?

Answer:ip accounting-list

 

49,Characteristics of static VLAN configurations include the following:

Secure

Easy to configure

Straight forward to monitor

Works well in networks where moves, adds, and changes are rare

 

50,These guidelines and restrictions apply to dynamic port VLAN membership:

You must configure VMPS before you configure ports as dynamic

When you configure a port as dynamic, spanning-tree portfast is enabled automatically for that port

You must turn off security on the static secure port before it can become dynamic

You must turn off trunking on the trunk port before changing it from static to dynamic