300-070 · Question #222
When an IP phone boots up, which mechanism provides the VLAN ID?
The correct answer is A. CDP. CDP (Cisco Discovery Protocol) is the mechanism that provides the Voice VLAN ID to a Cisco IP phone during boot. When an IP phone is connected to a Cisco switch port, the switch sends CDP advertisements that include the voice VLAN information. The phone uses this to tag its…
Question
When an IP phone boots up, which mechanism provides the VLAN ID?
Options
- ACDP
- BDNS
- CDHCP
- DTFTP
- EOption 150
How the community answered
(52 responses)- A90% (47)
- B6% (3)
- C2% (1)
- D2% (1)
Explanation
CDP (Cisco Discovery Protocol) is the mechanism that provides the Voice VLAN ID to a Cisco IP phone during boot. When an IP phone is connected to a Cisco switch port, the switch sends CDP advertisements that include the voice VLAN information. The phone uses this to tag its traffic to the correct VLAN before it requests an IP address. DNS resolves names to IPs, DHCP provides the IP address, TFTP serves the configuration file, and DHCP Option 150 tells the phone where the TFTP server is-but none of these provide the VLAN ID.
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