Topic 5 – Describe and configure a Cisco network to support VoIP
Power over Ethernet (PoE) is the ability for the LAN switching infrastructure to provide power over a copper Ethernet cable to an endpoint (Powered Device). This capability, once referred to as “inline power”, was originally developed and first delivered by Cisco in 2000 to support the emerging IP Telephony deployments. IP Telephones, like desktop PBX phones, need power for their operation and Power over Ethernet enables scalable and manageable power delivery and simplifies deployments of IP Telephony. As Wireless networking emerged, Power over Ethernet was also used to power these devices to allow for deployments in locations where local power access did not exist. While IP telephones and wireless access points are the most intuitive uses for PoE, the advent of 802.3af standardization of PoE opens the door to a new generation of networked-attached devices such as video cameras, point-of-sale devices, security access control (card scanners), building automation and industrial automation just to name a few. When a Cisco switch supply PoE to an IP phone?
A.whenever switch and IP phone are Cisco products.
B.when Cisco switch supports prestandard PoE and the IP phone supports 802.3af.
C.when Cisco switch and IP phone both support a common PoE method.
D.Only when both the switch and IP phone use 802.3af PoE.
This question tests the POE power supply. There are two POE power supply methods for the Cisco devices: one is the Cisco POE and the other is a standard-based 802.3af POE. The two methods of power supply are incompatible. Only when IP Phone and switches support the same POE method, switches can supply POE.
A: All Cisco switches support Cisco POE. The switch 3560 and above support 802.3af POE, while only 7971G-GE and 7970G IP Phones support 802.3af POE. When POE modes at both ends are the same, power in line can be provided.
B: For the same reason, only when switches and IP Phone support the same POE mode, power in line can be provided.
C: When switches and IP Phone support the same mode, power in line can be provided.
D: Both ends support 802.3af and Cisco POE, power in line can be provided.
What is the default VTP mode on Cisco switches?
This question tests the Cisco VTP mode.
Cisco VTP has three modes: Server Mode, Client Mode and Transparent Mode. The default VTP mode on Cisco switches is the Server Mode.
What are the three VTP modes on Cisco switches?
Answer: B C D
This question tests the Cisco VTP mode.
There are three VTP modes supported by Cisco switches: Server, Client and Transparent.
Whhich statement is true abou the difference between voice VLAN and native VLAN?
A.Voice VLAN uses untagged frames whereas native VLAN uses 802.1Q frames
B.Voice VLAN uses tagged 802.1Q frames whereas native VLAN uses 802.1P frames
C.Voice VLAN uses tagged 802.1Q frames whereas native VLAN uses untagged frames
D.Voice VLAN uses untagged frames only when no PCs are connected behind the phones whereas native VLAN always uses untagged frames
This question tests the relationship between voice vlan and native vlan, as well as that of 802.1q and 802.1p.
802.1q is the trunk encapsulation of Layer 2 frame, which has four bytes together, two tags and two control bytes. The first three bit of the control bytes stands for the 802.1p priority, that is, the COS value, which is used in QOS to mark the priority of data packets. Voice VLAN uses tagged 802.1Q frames but the common access interface is unable to receive 802.1Q frames. The configured interface of voice vlan is similar to a trunk, which is able to receive the data frame with 802.1q fields (tag of voice vlan). Native vlan is the special use of 802.1q, which refers to using the untagged data frames to stand for native vlan to load the untagged packets in avoidance of packet losses. So the correct answer is C.
Cisco ____protocol is used to inform the IP phone of its voice VLAN ID.
This question tests the modes of interacting voice vlan information between Cisco Switches and IP Phone. Cisco Switches uses CDP packets to inform the IP phone of its voice VLAN ID
If you need to take CCNA Voice 640-461 exam, do not miss reading 640-461 dump.