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642-813 Q&A – Prepare infrastructure to support advanced services (56-60)

Section4 – Prepare infrastructure to support advanced services

Refer to the exhibit. Which Catalyst switch interface command would be used to cause the switch to instruct the phone to override the incoming CoS from the PC before forwarding the packet to the switch?56

A. mls qos cos 2 override
B. switchport priority extend cos 2
C. switchport priority extend trust
D. switchport priority extend none
E. mls qos cos 2
F. switchport priority extend cos 11
Answer: B
Overriding the CoS Priority of Incoming Data Frames
You can connect a PC or other data device to a Cisco7960 IP Phone port. The PC can generate packets with an assigned CoS value. You can configure the switch to override the priority of frames arriving on the IP phone port from connected devices.
Beginning in privileged EXEC mode, follow these steps to override the CoS priority received from the nonvoice port on the Cisco7960 IP Phone.

Which two statements about a wireless repeater topology are true? (Choose two.)
A. A wireless repeater is an access point that is not connected to the wired LAN.
B. The repeater feature is only available in lightweight access point topologies.
C. The SSID of the root access point must be configured on the repeater access point.
D. This topology requires a 10 – 15 percent overlap between a wired access point and the wireless repeater.
E. This topology requires a 15 – 25 percent overlap between a wired access point and the wireless repeater.
F. To avoid interference, the repeater access point must use a different channel from what the root access point uses.
Answer: AC
Use APs in Repeater Mode
You can configure APs to act as repeaters. In this mode, the AP is not connected to the wired LAN. Instead, the AP is placed within the radio range of the AP that is connected to the wired LAN (the root AP). In this scenario, the repeater AP associates with the root AP, and extends the range of the radio coverage area. This enables Wireless Clients that reside away from the root AP to gain access to the WLAN network. You can configure either the 2.4 GHz radio or the 5 GHz radio as a repeater. In APs with two radios, only one radio can be a repeater. You must configure the other radio as a root radio.
When you configure an AP as a repeater, the Ethernet port on that AP does not forward traffic.
The advantage with the repeater mode in APs is that this mode helps to extend the radio coverage area of a WLAN in situations where connectivity to the wired LAN is not possible. Also, there must be a fifty percent overlap in coverage area with the root AP for the repeater mode to function.
Part of the configuration guide for setting up the wireless AP states:
In the next step, designate this SSID as an infrastructure SSID.
— If you created an infrastructure SSID on the root AP,
— create the same SSID on the repeater.

What are three examples of call control signaling? (Choose three.)
C. G.729
D. H.323
E. G.711
Answer: B,D,F
Call Control Signaling:
Packets belonging to one of several protocols-those used to set up, maintain, tear down, or
redirect a call, depending upon call endpoints. Examples are H.323, Media Gateway Control
Protocol (MGCP), and SIP (Session Initiation Protocol)
Incorrect Answers:
A: The is the protocol used to carry voice packet streams; it is not a signaling protocol.
C: These are codec standards used to compress a VOIP call.
E: These are codec standards used to compress a VOIP call.

In what three ways is QoS applied in the campus network? (Choose three.)
A. No traffic marking occurs at the core layer. Layer 2/3 QoS tags are trusted from distribution layer switches and used to prioritize and queue the traffic as it traverses the core.
B. IP precedence, DSCP, QoS group, IP address, and ingress interface are Layer 2 characteristics that are set by the access layer as it passes traffic to the distribution layer. The distribution layer, once it has made a switching decision to the core layer, strips these off.
C. MAC address, Multiprotocol Label Switching (MPLS), the ATM cell loss priority (CLP) bit, the Frame Relay discard eligible (DE) bit, and ingress interface are established by the voice submodule (distribution layer) as traffic passes to the core layer.
D. The distribution layer inspects a frame to see if it has exceeded a predefined rate of traffic within a certain time frame, which is typically a fixed number internal to the switch. If a frame is determined to be in excess of the predefined rate limit, the CoS value can be marked up in a way that results in the packet being dropped.
E. The access layer is the initial point at which traffic enters the network. Traffic is marked (or remarked) at Layers 2 and 3 by the access switch as it enters the network, or is “trusted” that it is entering the network with the appropriate tag.
F. Traffic inbound from the access layer to the distribution layer can be trusted or reset depending upon the ability of the access layer switches. Priority access into the core is provided based on Layer 3 QoS tags.
Answer: AEF
Three main types of QoS policies are required within the Campus:
1)Classification and Marking
2)Policing and Markdown
Classification, marking, and policing should be performed as close to the traffic-sources as possible, specifically at the Campus Access-Edge. Queuing, on the other hand, needs to be provisioned at all Campus Layers (Access, Distribution, Core) due to oversubscription ratios.
Distribution and edge switches can be configured to trust the COS markings of incoming traffic, rest the COS value to 0, or reset the COS value to a different value. These switches also perform the necessary functions to map the layer 2 COS values to a layer 3 TOS or DSCP value when sending traffic into the cloud.

Refer to the exhibit. On basis of the configuration that is provided, where will the trust boundary be established in this network?

A.at the PC
B.at the IP phone
C.at the access switch
D.at the distribution switch
Answer: C
The example shown is a properly configured switch where the trust boundary is being set at the access port on the switch itself. The “switchport voice vlan vlan-id dot1q” command enables voice VLAN on switch port and associated VLAN.
The “mls qos trust cos” command enables QoS (Quality of Services ) based on COS (Class of service).
The “switchport priority cos <priority>” value sets the priority values to frame coming from PC to switch port.

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