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Configuring VLAN for voice/data traffic separation

Current configuration:
I have a LAN of about 50 PCs and 50 VOIP phones. Domain is Windows 2003. There is only one CAT5e drop in every desk. The LAN cable goes from the wall to the phone and from the phone to the PC. All phones and PCs get IP addresses from the Windows 2003 DHCP server and they're all in the subnet. The phone system itself has a fixed IP of in this subnet. We are currently using analog lines with this phone system for external service. This configuration has been working fine this far. We have 2 Dell Powerconnect 2724 switches as main ones for the local LAN. They are both browser manageable and offer VLAN capabilities.

What is changing:
We are adding a T1 line with our current ISP and we'll switch to a SIP based service and eliminate the analog one. After this process we will run the voice service through T1 and we'll  continue running internet and data service with our current setup. However, the ISP has informed me that the phone system will need a different private IP and outside the subnet in order to separate traffic and run via T1. They say that all I need is a VLAN capable switch which I already have.

If I want to give the phone system the IP of how can I configure VLAN in order to make this work and not lose connectivity between the phone system and individual phones? Will individual phones need to be on the same subnet as the phone system? What is the best and simplest approach to this?

Thank you.
Network ArchitectureIP TelephonySwitches / HubsDell

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Last Comment

8/22/2022 - Mon

What switches do you have/use?
You could use the phone MAC address to assign them to a VOICE VLAN and have them on different network segments.
Marius Gunnerud

If you have Cisco switches you can do the following:

int gig0/1
switchport mode access
switchport access vlan 10
switchport voice vlan 20

Dell Powerconnect 2724 switches. I have not configured VLANs before so I'd need a bit more detailed suggestions. In addition there are other switches on the LAN that feed from the 2 main ones. Would they need their own VLAN configuration too or just the main switch is enough.
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William Peck

Info reference deals with how VLAN membership is assigned during discovery of cisco phones

The difficulty in you case is that you are assigning IPs from win2k3, integrating IAS and distributing different IPS along with VLAN membership aspart of the DHCP options.

Additional illustration

Is it possible to create a second subnet in AD and use fixed IPs for the phone sets and then somehow create a relationship btw the 2 subnets in Windows 2003?

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The phone software maker is Fonality based on Asterisk OS, hardware is Dell.
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In this case, usin QoS to prioritize voice type traffic might be what is needed.
Covers the type range.