This is a "how does it work?" question. There is no problem to be solved.
My assumption has always been that VLANs were handy for segmenting broadcast domains (keepingn subnets reasonably small) and for isolating subnets. The two objectives are likely disjoint in that the first objective may not at all include the second. That is, one wants limited-size subnets but wants them to be able to intercommunicate.
My understanding is that one needs a router to accomplish the intercommunication. Whether, in practice, this is a separate router or part of a more-capable switch, both seem likely.
So, the questions:
- What are a few of the most typical ways to set up multiple VLANs and then allow them to communicate from one to the other?
- Is this indeed a common situation?