What do I need to do to add a new subnet to be used  exclusively by VoIP phones and VLAN the switches + more?

Posted on 2006-07-07
Medium Priority
Last Modified: 2010-04-12
I am trying to change our configuration with these steps.  However, I might be missing additional things that need to be done and I have little knowledge of VLANs, configuring managed switches, and especially having 2 subnets.  We are currently running out of IPs on our 192.168.1.x network for data and I wanted to setup a VLAN for VoIP phones that will be added.  I also need to get more IPs for data though.

Also, what we are doing here is connecting to a new building in our backyard that we purchased.  The building is connected via fiber and Dell switches are on each floor.  We also have an Iwatsu phone system in each building which gives us an IP campus scenario.  The new building will be VoIP and digital phone mixed and the old building is just digital.  

Ok, here are my thoughts...

1) Adding a new second subnet (a 192.168.2.x) network (we are currently using 192.168.1.x for data)
2) VLAN the Dell switches to work with our current subnet and a new subnet (switches are connect via fiber modules and are Dell PowerConnect 24-port managed switches and 1 Dell PoE switch for IP phones)
3) Have our new IP phones run on the new 192.168.2.x subnet and connect them into the Dell PoE switch
4) Understand what the heck we are doing and what needs to be done to our Watchguard Firebox x500 gateway/firewall, if additional NIC cards are needed, and changes that need to be made on our Windows 2003 DHCP server. (we are in an all Windows 2003 Server environment).

Any help is appreciated

Thank you
Question by:draracle
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LVL 36

Accepted Solution

grblades earned 2000 total points
ID: 17079582
Currently you are using for your data network and are running out of IP's.
I would change the subnet mask to That way your data network can use through to
You should be able to make this change on your windows server and in the DHCP configuration without affecting any other machine.
Remember you also update the subnet on anything with a fixed IP address (firewall, servers, etc...)

Then setup a separate VLAN using
You wont need to have the firebox connected to the voip vlan as the phones wont need internet access. You will want some form of dhcp server so the phones can get an IP address. The phone system may offer this service.

Author Comment

ID: 17080801
What if I want an IP phone to be offsite...wouldn't I need to give the IP phone a static IP internally and add it to the NAT table so it could get through the PBX?  I am also being advised not to change the subnet mask because we are at 192.168.1.x and not 192.168.0.x at the present.
LVL 36

Expert Comment

ID: 17080875
If you want a phone to be offsite then there should be no NAT between the phone and the PBX. This is because most PBX's use SIP which does not work well through NAT and results in one way audio.
It depends where the outside phone is actually going to be located. If it is going to be at a different office location then you could setup a VPN between the two offices. includes 192.168.1.x so it will still work if you change the subnet mask.
The only issue you will find is that any computers given an IP outside 192.168.1.x will not be able to talk to other machines which have not yet had their subnet mask updated.
If you update all the servers first then during the update the only machines which wont be able to talk directly would be the client machines with each other which is something you normally wont do anyway.

Author Comment

ID: 17083404
I think we will give this a try.  Thanks for your help

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