Is bridging not the term when connecting two networks together. In essence connecting vlans together (whether it be via a router or internally on a switch) is a form of bridging although that term really doesn't mean a whole hill of beans in today's networks. Dig deep to old school days.
Try this - 24 Port Switch
P1-10 Untagged Members of VLAN10
P11-22 Untagged Members of VLAN20
P23 - Untagged Member of VLAN30
P24 Tagged Member of VLAN 10,20,30
P24 into a VLAN tagging aware router, in my normal case a Cisco or Zyxel USG series.
Oh my. You completely missed it. Was talking about a server not a hardware router. I can do similar with VMware and hyper-v nothing to try there I know what it does and how it works. Like I said you need an os that supports it.
Trying not to add any other pieces of networking hardware other than the switch itself or the servers to stay on topic.
There are several key pieces that we don't know. First what is meant by secure (inside attack, outside attack, malware attack, who knows maybe by this vague description he wants to know if he is secure from a std his girlfriends sister has who he never met...might as well be, we have about enough information to possibly to come to a conclusion about that). Second we know very little about his network, it's got vlans and what are we supposed to be able to tell with that information? I have some or all of the parts to put you in orbit, is it possible..that is similar to all of the information that was given in the initial post. Third, what exactly is he trying to accomplish? By attempting to understand the the limited information given he may not have the proper hardware and/or software in place to make this work.