VLAN VoIP and LAN configuration over multiple switches

Question

Some background: I currently have:

• Switch A Main 48 port 1Gbps (DLink)
• Switch B 10Gbps Backbackbone (DLink)
• Switch C 24 port 1Gbps (DLink)

Telephone Switch 1-24 port phone switch connected to a 3rd-party supplier's switch.

My setup is as follows:

PC's --- Switch A  ----- Switch B (and servers) ----- Switch C  --- PC's

I have PCs connected to Switch A. These connect to those on Switch C via Switch B where the servers are also connected

I want to plug the phone system into Switch A, and then be able to plug a telephone into a port on Switch C and get VOIP.

I've set up a small test on a single switch using the following VLan's

1 - default 
20 - Data
50 - Voice

Which worked perfectly. I had both networks plugged in and all seemed to be happy.

So the questions ...

• Do I need to configure the VLANs on all switches or just those with a phone / PC connected?
• Do the backbone connections need to be tagged in a VLAN or will leaving it in the default be enough?

I also have a number of other switches that are connected to Switch A. These are data-only and do not need telephone access. Am I correct in assuming that simply tagging the ports as data only will be sufficient?

Thanks

Pete

Answer 1

If all your connections between switches are layer 2, then yes, you need to trunk all VLANs across your backbone switch.

The ports connecting your switches to the backbone will be configured as trunks, and you will tag VLANs. The ports connected to single devices (phones or PCs) will be untagged on the appropriate VLAN.

If you have phones and PCs sharing a single port, then those ports will have the data VLAN untagged and the voice VLAN tagged.

If you're absolutely sure that some switches will never need phones, then the connecting ports will have the data VLAN untagged.