|I need some of the users in the dafault VLAN to use the VoIP router as their gateway to Internet.|
In my world, we keep them separate because the VoIP traffic leaves the network, passes through the VoIP Controller and then into our PBX. The controller would drop the data traffic down a bit bucket and that would be the last you'd see of it since it doesn't belong.
You state, "As I don't have many clients in the network, I have everything in the same subnet."
Two issues here:
1) If you don't have many clients then why, for goodness sake, do you want to shove data traffic in with the VoIP? VoIP is a higher priority type of traffic (QoS) so mucking your VoIP network up with data traffic makes no sense when you don't have to.
2) Your data and VoIP subnets should be different and separate.
VLAN 1 = 192.168.1.0/24
VLAN 2 = 192.168.2.0/24
You should have a DHCP server configured in each and no route's between. One SOHO Router for each VLAN would be sufficient to do the DHCP and provide firewall.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.