Voice Support Questions
Here you will find answers to Voice Support Questions
(Questions 1 to 4 use the same picture)
Question 1:
You work as a network technician, study the exhibit carefully. What is the effect on the trust boundary of configuring the command mls qos trust cos on the switch port that is connected to the IP phone?
A – Effectively the trust boundary has been moved to the IP phone.
B – The host is now establishing the CoS value and has effectively become the trust boundary.
C – The switch SW is rewriting packets it receives from the IP phone and determining the CoS value.
D – The switch SW will no longer tag incoming voice packets and will trust the distribution layer switch to set the CoS.
Answer: A
Explanation:
The “mls qos trust cos” command is used to configure the port trust state (by default, the port is not trusted). By using this command, you can configure the switch port to which the telephone is connected to trust the CoS labels of all traffic received on that port.
(Note: All current Cisco IP Phones include an internal three-port Layer 2 switch therefore you can think an IP Phone as a switch and network administrators generally accept a Cisco IP Phone as a trusted device.)
Question 2:
If you are a network technician, study the exhibit carefully. Which switch interface configuration command would automatically configure quality of service (QoS) for voice over IP (VoIP) within a QoS domain?
A. auto qos voip cisco-phone
B. mls qos trust
C. switchport priority extend cos 7
D. switchport priority extend trust
Answer: A
Explanation:
The command “mls qos trust” is used to configure the port trust state (by default, the port is not trusted).
The command “switchport priority extend cos 7″ sets the IP phone port to override the priority received from the PC or the attached device (7 is the highest priority).
The command “switchport priority extend trust” tells the Cisco IP Phone to trust the CoS value of the connected PC without remark all packets sent form PC to CoS 0, by default.
Question 3:
Study the exhibit carefully. Which statement is true about the voice traffic coming to the switch access port that is connected to the IP phone?
A. The voice VLAN must be configured as a native VLAN on the switch.
B. A PC connected to a switch port via an IP phone must support a trunking encapsulation.
C. The traffic on the voice VLAN must be tagged with 802.1p encapsulation in order to coexist on the same LAN segment with a PC.
D. A PC connected to a switch port via an IP phone is unaware of the presence of the phone.
Answer: D
Explanation:
The voice VLAN can be configured over a unique voice VLAN (known as the voice VLAN ID or VVID) or over native VLAN -> A is not correct.
The ports k between PC and IP Phone are always functioned as access-mode switch ports so there is no need to support a trunking encapsulation -> B is not correct.
The traffic on the voice VLAN can be tagged with 802.1p encapsulation or 802.1q encapsulation -> C is not correct.
Most Cisco IP Phone models operate as a three-port switch as shown below. Nowadays, the voice traffic and data traffic will normally be on different IP subnets and the IP Phone is unaware of the presence of the phone.
Question 4:
Study the exhibit carefully. Which statement is true when voice traffic is forwarded on the same VLAN used by the data traffic?
A. Quality of service cannot be applied for the voice traffic.
B. The voice traffic cannot be forwarded to the distribution layer.
C. Port security cannot be enabled on the switch that is attached to the IP phone.
D. The voice traffic cannot use 802.1p priority tagging.
Answer: D
Question 5:
Which two codes are supported by Cisco VoIP equipment?
A. G.701 and G719
B. G.711 and G.729
C. G.721 and G.739
D. G.731 and G.749
Answer: B
Question 6:
Study the exhibit carefully, then tell me what is the problem with this configuration?
A – Spanning tree PortFast cannot be configured on a port where a voice VLAN is configured.
B – The switch port must be configured as a trunk.
C – Sticky secure MAC addresses cannot be used on a port when a voice VLAN is configured.
D – Spanning tree PortFast cannot be configured on a port when a sticky secure MAC address is used.
Answer: C
Study the exhibit carefully. Which statement is true about a voice VLAN
segment?
A. Physically the voice network and the data network are separate.
B. The voice traffic will normally be on a different IP subnet than will th
C. End user intervention is necessary to place the phone into the prop
D. The same security policy should be implemented for both voice and data traffic.
E. The data VLAN resides in the native VLAN. F. None of the other alternatives apply
ti 3.3 say right answer is B
passguife 3.21 says right answer is E
Wat is right answer?
@akaEvgen
I prefer B, voice vlan usually use a different ip address space besides the host.
talking about E, usually there is no “native vlan” in a voice access port, because native vlan is usually refered in trunk port.
@bypasser
Thanks.
From official certification guide page 310
Right answer is E. Because data reside in access vlan when “switchport voice vlan none”
All other situation the data vlan is a native vlan
This question is a bit misleading, in that there are multiple things wrong with the config as per the diagram. I guess that if one can ignore all the other stuff then answer would be C.
Cisco Website on 3560
http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_25_se/configuration/guide/swtrafc.html
You cannot configure static secure or sticky secure MAC addresses in the voice VLAN.
——————————————————————————–
Note Voice VLAN is only supported on access ports and not on trunk ports, even though the configuration is allowed.
Study the exhibit carefully. Which statement is true about a voice VLAN
segment?
A. Physically the voice network and the data network are separate.
B. The voice traffic will normally be on a different IP subnet than will th
C. End user intervention is necessary to place the phone into the prop
D. The same security policy should be implemented for both voice and data traffic.
E. The data VLAN resides in the native VLAN.
F. None of the other alternatives apply
Has to be E–the voice vlan is the tagged vlan, data is the untagged vlan. Can’t place voice and data with a sticky-mac so that’s that as they say…
Q4: I think the answer should be corrected as:
D. The voice traffic CAN use 802.1p priority tagging.
it is written as “can not” above, but it can use 802.1P priority tagging to give voice traffic a
higher priority and forward all voice traffic through the native (access) VLAN.
Obviously i cant see the config but.
on a port you will likely do 2 commands:
switchport access vlan 10 (for example)
switchport voice vlan 20.
this means data traffic is in vlan 10, and will be tagged, so it will nto be on the native vlan (which shoudl be pruned off the trunk anyway)
So, id go with B.
Also, onl the basis that a different vlan has a different subnet assigned to it. as voice will require separate CoS, it will have a separate vlan. So yes. B.
Thank you for another great article. Where else could anyone get that kind of information in such a perfect way of writing? I have a presentation next week, and I am on the look for such information.
@akaEvgen
I actually like answer E for that question. While I can’t see the exhibit, if it is configured with:
switchport access vlan 10
switchport voice vlan 20
The voice traffic resides in the auxiliary vlan 20 and the data traffic resides in the native vlan 10.
QUESTION
VoIP—-How does the switch carry vlan information for the IP phone when the interface connecting the phone has been hardcoded as an access port???
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Q3. I couldn’t understant why answer 3 is ok . I found out on cisco wbe that when “switchport port-security mac-address sticky” is configured on voip port “the maximum number of allowable MAC addresses on this port should be changed to three”.
Configure IOS Catalyst Switches to Connect Cisco IP Phones Configuration Example
http://www.cisco.com/en/US/products/hw/switches/ps4324/products_configuration_example09186a0080722cdb.shtml
Very informative post. Thanks for taking the time to share your view with us.
You certainly deserve a round of applause for your post and more specifically, your blog in general. Very high quality material
..The Cisco7960 IP phone contains an integrated three-port 10 100 switch. ..Because a Cisco7960 IP phone also supports connection to a PC or another device an interface connecting a Catalyst4500 series switch to a Cisco7960 IP phone can carry a mix of voice and data traffic.
I find myself coming to your blog more and more often to the point where my visits are almost daily now!
Very informative post. Thanks for taking the time to share your view with us.
Can anyone say me if the answeres of exam are the same that are posted here?
You certainly have some agreeable opinions and views. Your blog provides a fresh look at the subject.
I like the pictures of the IP phone’s being used in these diagrams, very realistic!
I am not sure about the last question!! Is that valid only with Cisco IP phones, cause I find it strange.
we use sticky on all our switchports and all are configured with vlan voice.
However , we use Avaya , not Cisco phones.
@Seattle
There are different modes of Voice and Data VLAN access ports (802.1q, etc) , some of them place voice in VLAN 0, some place data in native VLAN, others in access VLAN. So E cannot be the right option.
Regards,
Sarah G
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Que pensamiento simpГЎtico
Really great article with very interesting information. You might want to follow up to this topic!?! 2012
Really interesting blog, keep up the good work!
Thanks for tris interesting information! I found it very useful =)
Hi guys
I`ll make my exam next week, i want to know how much(generally) of question about wireless and voice appers on the exam ?
Already talked to some people and I was told not appear more than two questions from each topic, this is true?
Thank you
Choose two. The network administrator will be able to configure VLANs of local significance on this switch. VLANs can only be added to the VLAN database on this switch by a VTP advertisement. All VLANs that are configured on this switch will be sent to all other switches in the same VTP domain.
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Question Number 6 – SHENANIGANS! I successfully implemented port security using mac-address sticky command with a voice vlan on the port. See below.. Cisco 3750!
interface FastEthernet2/0/24
switchport mode access
switchport voice vlan 210
switchport port-security maximum 2
switchport port-security
switchport port-security mac-address sticky
switchport port-security mac-address sticky 0021.9b6b.1449
switchport port-security mac-address sticky 3cb1.5b11.2c54 vlan voice
spanning-tree portfast
end
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Can someone please explain the answer of Q6. I am gonna appear for SWITCH in 3 days!! Please!!
I have a doubt about question #1. According to you, the command “mls qos trust cos” will move the trust boundary to the IP phone. However, what that command really does is move the trust boundary to the distribution switch because it’ll trust COS from both the phone and the computer. I believe the correct command for answer A is “mls qos trust device cisco-phone”, because it’ll trust COS from only the phone and tell the phone to mark the COS from the computer as 1.
Sorry I was wrong. I did a little more research and found that “mls qos trust cos” will trust COS coming only from the tagged packets, which is obviously the voice vlan, and the untagged data packets will not have a COS value. The command “mls qos trust device cisco-phone” is actually a macro that will put the following commands in if it detects an ip phone via CDP:
-mls qos trust dscp
-mls qos trust ip-precedence
-mls qos trust cos interface command.
Thanks inspiring me to look more into it.
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