You manage a network that has a Voice over IP phone system and has a voice VLAN that all the VoIP phones connect into. You install a new VoIP phone and receives an IP address in the wrong subnet. What is the most likely cause of this problem?

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Multiple Choice

You manage a network that has a Voice over IP phone system and has a voice VLAN that all the VoIP phones connect into. You install a new VoIP phone and receives an IP address in the wrong subnet. What is the most likely cause of this problem?

Phones in a VoIP system rely on a dedicated voice VLAN, which has its own subnet and DHCP scope. When a newly connected VoIP phone ends up with an IP address from a different subnet, the most likely reason is that the phone’s switch port is not placing traffic into the voice VLAN. If the port is misconfigured (or the VLAN tagging on the trunk is incorrect), the phone ends up on the data VLAN and receives an IP from that subnet instead of the voice VLAN’s subnet. DHCP misconfiguration could cause IP issues, but it would typically affect more than just a single new device or show symptoms beyond ending up in the wrong subnet. An IP address conflict would produce duplicate addresses rather than a subnet mismatch. In short, the root cause here is the phone being on the wrong VLAN due to port/VLAN tagging configuration. To fix, verify the switchport is assigned to the voice VLAN and that VLAN tagging is correct on the link carrying the VoIP phones.

Phones in a VoIP system rely on a dedicated voice VLAN, which has its own subnet and DHCP scope. When a newly connected VoIP phone ends up with an IP address from a different subnet, the most likely reason is that the phone’s switch port is not placing traffic into the voice VLAN. If the port is misconfigured (or the VLAN tagging on the trunk is incorrect), the phone ends up on the data VLAN and receives an IP from that subnet instead of the voice VLAN’s subnet.

DHCP misconfiguration could cause IP issues, but it would typically affect more than just a single new device or show symptoms beyond ending up in the wrong subnet. An IP address conflict would produce duplicate addresses rather than a subnet mismatch. In short, the root cause here is the phone being on the wrong VLAN due to port/VLAN tagging configuration. To fix, verify the switchport is assigned to the voice VLAN and that VLAN tagging is correct on the link carrying the VoIP phones.

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