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IP Office Platform H.323 Telephone Installation
VLAN and IP Phones
The use of VLAN allows separate collision domains to be created on Ethernet switches. In the case of IP Office and IP Phones the advantages are:
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It allows PCs to continue in the same IP subnet while IP Phones can use a new and separate IP addressing scheme.
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Broadcast traffic is not propagated between the PC data network and the IP Phones voice network. This helps performance as otherwise broadcast traffic must be evaluated by all receivers.
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VLAN networking and traffic prioritization at layer 2 are closely bound together in the same 802.2 standard. It is therefore easier to maintain L2 QoS when using a VLAN.
The table shows the three ways in which VLAN can be deployed with an Ethernet Switch. The first two methods require only elementary configuration, and since this document assumes both PC and IP Phones share the same Ethernet port, the focus will be the third method (overlapping).
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Type
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Description
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Advantages
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Disadvantages
|
|---|---|---|---|
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No VLAN
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Both Voice and Data occupy the same collision domain
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Simple Configuration
|
PC broadcast traffic adverse effect on Voice traffic.
Requires two (2) ports per user; one for IP Phone and one for PC)
|
|
Physical VLAN
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Separate VLAN for data and voice
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Simple configuration
|
Requires two (2) ports on switch; one for IP phone and one for PC
|
|
Overlapping VLAN
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A single port on the switch carrying both the IP Phones as well as the PC traffic
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Requires only a single port for both PC and IP Phone
PC broadcast traffic cannot adversely effect Voice traffic
|
Complex configuration
|