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VLAN Question?

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SpaceA

Technical User
Dec 19, 2007
32
US
How does the network recognize a device when it is plug into the network? I have two sets of IP address, Class C address 165.xxx.xxx.xxx for computer and other network device and Private address 10.xxx.xxx.xxx for VoIP use only. How does it work when I plug my IP phones into the network it give me a 10.x address and when I plug my computer into the same jack it gives me a 165.x address? How does this work, where is the setting to tell the device to pickup different address? Thanks in advance.
 
People in that situation use a "voice vlan" and the default vlan. So based on tagged frames or not tagged frames, they go to the appropriate vlan. Whoever your voice vendor is should know how to do this, as it's really common practice.
 
The site where i'm at the moment has a nice example.

They have here a data network of there own and we provided the voice part.

Vlan 1 (default) is used for the cusomers data lan.
Vlan200 is used for our voice network.

Now a port on switch where a pc and a phone are connected looks as following:

interface FastEthernet0/3
switchport mode access
switchport voice vlan 200

Then there is also a port connected to a switch of their own which has their own dhcp server on it. This port is set in trunking mode wich allows all vlan's

Then there is a second port that is connected to our voice network. This port is also a trunk but only allows vlan 200.

What happens when a cisco phone is plugged in to port 3 is than the switch recognises the phone (cisco-cisco :D ) and automaticly send all the traffic of the phone to vlan200.
Which goes to the trunk with vlan 200 and here it finds the dhcp server of the voice network.And so it is getting an ip address from within the voice network.

On the otherhand when a pc is connected the switch will see this as a "not voice" device and will put all the traffic of this one in vlan 1. And goes out on the trunk port that is connected to the part where their own dhcp server is
And this way it gets a address from their own dhcp server.


I hope this clarrifies you question
 
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