I'm the resident IT guy in an office with about 20 workers, amongst 3 separate companies who sublet an office.  We are wired with 24 ethernet ports dotted around the offices that all lead to a patch panel in my office. They are connected to 4 unmanaged switches into our ISP-supplied, cheap, router. (Internet is provided by a regular ADSL2+ provided by BT in the UK).  The problem is we are all one network, despite being separate companies, which is a security concern so we want to separate the logical/virtual networks (presumably, VLANs), but our current basic router doesn't support port-based VLANs.  I'm consider two options to isolate the networks, and I'd like advice which will do the trick:   A enterprise 4-port router (perhaps a  or ) that supports port-based VLANs, and plug our existing unmanaged switches into that:   (obviously, I would restricted to 3-4 VLANs, but that's fine Or, a large 24-port managed switch (like a Cisco), that supports allows me to define which of it's many ports belong to which VLANs.   I understand that this can just work in a "router-on-a-stick" configuration. Crucially, my network cupboard is too small to fit a typical 24 port switch, It's only got about 22cm depth.
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