VOIP and LAN in the same network

Hi, I’m deploying FreePBX Voip on a very small network, 15 users, maybe 3-4 concurrent calls max at any given time.
For such a small deployment, can I get away with putting the VOIP on the existing network and vlan?
How critical is it to isolate VOIP and DATA network? Has anyone done this? what does the conventional wisdom say?

Thank you.

@kfkenshin : I have deployed FreePBX Voip on the existing data network in my office. There are around 12 people using the network and I have around 6-7 extensions. It seems to be fine, there doesn’t seem to be a problem in the connection quality because of the network. There was a voice quality issue with a-law and u-law codecs, but once I changed to g722 codec, the quality was really good.

TIP : I deployed asterisk from a docker system, which made the installation process very simple.

My last 5 implementations were all on flat networks. Including the current one. 50 workstations and 40 phones. No issue whatsoever. Remember that VLANs are not for performance.The wire can only move so much. If possible, have your edge device prioritize the traffic in and out of the PBX to your SIP provider.

Totally flat network here. 200 and something PC’s, 115 phones.
No problems so far, although do plan to redesign the network in the next few months.

that gives me some comfort level.
performance aside, are we worried about security?

Very good point raised by @andersonhaulage vlan has nothing to do with performance, and QOS is overrated.

On a non-asterisk system, we have around 100 phones and over 100 computers on the same flat network without any problem, and this includes IPSec WAN links. We run about 5000 voice minutes per day.
Just ensure you have high quality network switches and good cabling etc, monitor for packet loss and keep within your bandwidth.

Security isn’t an issue so long as you keep the doors closed. Don’t open the voip to the outside world at all. Port forward from the ITSP IP addresses and ports only. Route intra-site traffic over the VPN.