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myCCNP Switch 300-115 > Practice Q's - Voice > Flashcards

Practice Q's - Voice Flashcards

1
Q

When using auxiliary VLANs, how is a phone configured with the appropriate VLAN to join?

A. the administrator configures the phone with CLI

B. the switch connected to the phone provides the VLAN

C. the PC attached to the phone provides the VLAN information

D. a VMPS server provides the VLAN for the switch and phone

A

Answer: B

Explanation:

When using auxiliary VLANs, the switch connected to the phone provides the VLAN to the phone.

IP telephones typically have a built in 3-port 10/100 hub. One port internally attaches to the phone, one port is attached to the switch access port, and the other is used to connect to the workstation. The PC attached to the switch port via the IP phone is unaware of the presence of the phone

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2
Q

What Cisco switch feature allows IP phones to be automatically placed into a separate VLAN from data traffic?

A. marking

B. AutoQoS

C. private VLANs

D. auxiliary VLANs

A

Answer: D

Explanation:

Auxiliary VLANs allows IP phones to be automatically placed into a separate VLAN from data traffic. The information the phones need regarding this voice VLAN is provided by the switch. This allows the data and voice traffic to use the same physical topology but remain logically separate. The following is an example of the commands that should be executed on the switch to instruct it to provide this information to the IP phone by CDP:

  • Switch> (enable) set port auxiliary vlan 2/1-3 222

This command creates the auxiliary VLAN 222 and adds ports 2/1 to 2/3 to the VLAN.

Private VLANs are not used for voice traffic. Private VLANs are secondary VLANs created by an administrator that are not accessible by other secondary VLANs.

Marking is the process of setting the Class of Service (CoS), IP precedence, or DSCP of a packet to a specific value that will provide appropriate QoS throughout the network. It is not involved in separating voice and data traffic.

Auto QoS is a method of configuring commonly used QoS features on a Cisco switch with a single command. It is not involved in separating voice and data traffic.

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3
Q

Which Cisco switch feature enables IP phones to be assigned IP addresses from a different subnet than the workstation attached to the same port?

A. Auxiliary VLAN

B. 802.1P

C. 802.1Q

D. in-line power

A

Answer: A

Explanation:

Auxiliary VLANs can assist in the deployment of Cisco IP telephones by allowing a Catalyst switch access port to support the data device on one VLAN and have the IP telephone assigned to a different VLAN. The auxiliary VLAN ID is not required to match the native VLAN associated with the access port of the switch. Therefore, the two port attached devices (the phone and the workstation) can be on two different broadcast domains or IP subnets. Some Cisco Catalyst switches provide the auxiliary VLAN feature that provides the automatic assignment of an IP telephone to a VLAN. This auxiliary VLAN feature is also known as the voice VLAN feature

IP telephones typically have a built in 3-port 10/100 hub. One port internally attaches to the phone, one port is attached to the switch access port, and the last port is used to connect to the workstation. The switch uses CDP on a port on which an auxiliary VLAN has been configured to advertise 802.1Q and 802.1P information. The attached IP telephone can use the advertised information to learn which VLAN ID and priority tag to use. The default Class of Service (CoS) value for incoming traffic is 0.

Having the telephone and the data device use different frame types and belong to different VLANs allows the administrator to place the telephones on their own subnet. Voice traffic on a separate VLAN is less likely to contend with the data devices.

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4
Q

When provisioning bandwidth for an IP telephony network, which elements are unique to an IP telephony call? (Choose two.)

A. voice stream

B. IGMP packets

C. call-control signaling

D. routing protocol packets

E. speed of the segment to the telephone

A

Answer: A,C

Explanation:

Bandwidth provisioning for an IP telephony call consists of the voice stream traffic and the call control traffic. These elements are unique to an IP telephony call.

The network infrastructure should be examined to see if the required bandwidth exists to support the voice and call-control applications. The sum of the bandwidth necessary for each major application, including voice, video, and data, should not exceed 75% of the total available bandwidth for each link. Voice traffic can be characterized as:

Voice packets are typically around 60 to 120 bytes in size. For good voice quality, packet loss should be less than 1 percent and delay should be no more than 150 ms.

The IP telephony voice call-control procedures also generate traffic. The call control procedures are in the areas of call setup, maintenance, redirect, and tear down. There are special protocols such as H.323 and Media Gateway Control Protocol (MGCP) that handle these procedures.

Voice applications are delay-sensitive. Speech is sampled by voice processors referred to as a codec (coder/decoder). Then the digitized voice-sample outputs of the codecs are sent into the network towards the receiver at regular intervals in real-time transport protocol (RTP) packets. If these packets containing the voice samples are delayed for any reason behind other data traffic, the quality of the voice conversation suffers.

The transportation of these voice applications in RTP packets through the IP network handled by

H.323 protocols and devices is referred to as Voice over IP (or VoIP for short).

The following are other network and design considerations besides bandwidth relating to IP telephony infrastructure support:

Internet Group Management Protocol (IGMP) is used for managing the membership of IP multicast groups and is not an element unique to an IP telephony call.

Routing protocol packets (RIP, OSPF, and EIGRP) are used by routers to share routing information, and are not elements unique to an IP telephony call.

The speed of the segment to the telephone is important to VoIP, but that is not an element unique to an IP telephony call.

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5
Q

What feature allows the administrator to put phones into a separate logical network from the data network while keeping both in the same physical network?

A. auxiliary VLANs

B. queuing

C. 802.1Q

D. marking

A

Answer: A

Explanation:

Auxiliary VLANs allows the data and voice traffic to use the same physical topology but remain logically separate. The information the phones need regarding this voice VLAN is provided by the switch. Auxiliary VLANs allows IP phones to be automatically placed into a separate VLAN from data traffic.

Queuing is the process of placing traffic in appropriate queues depending on the class of traffic.

Marking is the process of setting the CoS, IP precedence, or DSCP of a packet to a specific value that will provide appropriate QoS throughout the network.

802.1Q is a trunking protocol used to allow traffic from multiple VLANs to pass through a single link and still be logically separate.

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6
Q

What feature carries information about the Voice VLAN to a Cisco Phone?

  1. SIP
  2. LLDP
  3. CDP
  4. Skinny Client Control Protocol (SCCP)
A

Correct Answer: C

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7
Q

Which two statements about configuring a voice VLAN on a switch port are true? (Choose two.)

  1. The port must be operating in untrusted mode.
  2. Tagged traffic is not supported.
  3. It must be configured separately from the VLAN that carries data traffic.
  4. If the port is trusted, data traffic that passes through the Cisco IP Phone maintains its QoS values.
  5. The port must be operating in trusted mode.
  6. Cisco Discovery Protocol must be disabled on the switch port.
A

Correct Answer: CD

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8
Q

Which two statement about voice VLANs are true? (Choose two.)

  1. The VLAN number must be in the range 2000 through 4096
  2. They support static source MAC address
  3. They require PortFast to be enabled manually on the interface
  4. When they are enabled, all CoS values in incoming traffic are untrusted
  5. They are disabled by default
  6. When they are enabled, all untagged traffic is assigned a CoS of 5
A

Correct Answer: EF

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9
Q

Which protocol is used to propagate voice VLANs to a Cisco phone?

  1. DTMF
  2. SKINNY
  3. SIP
  4. LLDP
  5. Cisco Discovery Protocol
A

Correct Answer: E

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myCCNP Switch 300-115 (73 decks)

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