Theoretically you may achieve prioritization with or without separate VLANs. QoS may work both, by IP address (or range), or by Protocol/Port. However, from the management perspective, it's better to split two "environments" into the separate VLANs and Subnets.
Now some questions. What switch do you have for your PCs and phones? Is it Cisco switch? If it is, what model?
If you have Layer 3 switch (Catalyst 35xx/36xx/37xx series switch or higher), then you can do VLANs and routing on the switch itself. If it's Layer 2 switch (Catalyst 29xx series. etc), then you may configure the "uplink" port (port, connects to the router) as a 802.1Q trunk, and do routing between VLANs on the router. Here is a link to examples:
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.