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New Member

Cisco vlanning with voice and data


Please could someone advise me on the following. Any response will be greatly appreciated!

I have 14 switches Layer 2, and 1 Layer 3 core.

The setup is pc - phone - switch on one cable.

2 subnets for Users

                     vlan 1

                     vlan 2

2 subnets for Voice

                              10.1.3/24 vlan 3

                              10.1.4/24 vlan 4

What needs to be done, as there are over 300 users.

Is it possible that for example on half of the switches i could have one user and voice vlans.

and on the other 7 switches, have the other user and voice vlans

and have everything inter-vlanned at the core switch. So one phone in vlan 3 could communicate with another phone in vlan 4 for example ?

Unfortunately getting everyone on one range is not an option.

Thanks !

Everyone's tags (3)

Cisco vlanning with voice and data

Hi Steven,

the first thing i would do is to check that no inter-vlan routing is possible on your switches (except the core) and definitely increasing the number of data subnets. If you really have 14 Layer 2-only switches your biggest problem is the amount of broadcast packets and it is the first one you need to address.  If the core layer router support layer 3 you have no to worry about inter voice vlans comminucation (vlan 3 and 4) but i honestly see a good idea to take pen and paper and to design everything including STP, subnetting, Uplinks and so on.

Can you tell me more about the topology? Will you manage everything by VTP or manually?

Not too big network.. no worries!!!


New Member

Cisco vlanning with voice and data

Thanks for your prompt response.

Yes, only the Core can inter-vlan route.

I wont be able to change any of the subnet addresses, as these are set up by another party.

I will look into the broadcasting scenario.

I definately will be looking into the design, diagramming it out and all that..

I think the setup of vlans will be done manually, but I could look into VTP

I have my CCNA aswell.

Ive just never done a voice setup, and was worried that it wouldnt be possible for the data / voice in all the different vlans to communicate together.

I thought that you had to have a native vlan for the pc's and having to match that native vlan on all switches, would end up being able to use only the one subnet.

but if you can set it up with an actual vlan tag for data and voice, and leave the native out.


Switch 1- 7


Voice VLAN 3

Native 10

Switch 8 - 14


Voice VLAN 4

Native 10

and have everything inter-vlan at the core, it should work ?


Re: Cisco vlanning with voice and data

I would be very careful with the VLAN native in your domain. Since it is not a good practice to use VLAN 1 for your production environment, just leave the vlan 1 as the native and would concentrate on these reccomendations:

after this, just set all the switches in transparent mode (better manually managed at the beginning) and create your vlans across your switches

a) Vlan X for PC

b) Vlan Y for PC

c) Vlan 1 as native... (don't touch it )

d) Dot1Q as trunks

e) Vlan for management

f) Prune all the uplinks/trunks with an allowed vlan list

g) Define the core network config

h) Vlan W for voice

i) Vlan Z for Voice

l) CDP enabled

etc etc...

Believe me i don't want to be rude but you are quite lucky !! You just told having a relevant layer 2 infrastructure and a CCNA... Concidence wants that to start achieving your CCNP you have a full Layer 2 exam (SWITCH) !!!!!


Your infrastructure is a fantastic "lab" and by the way on that book there are many answers to your questions.

Good Luck