Say you have a 24 port switch, and you're only using 10 of the ports.Now you need to add another subnet, but it will only need 8 switchports.So you can either go out and buy an 8 port switch, or you can use vlans on your existing switch.Every switch operates in a vlan, usually vlan1 (which you should always change before you even use the switch).So now, you can leave 10 ports in the existing vlan, and assign 8 of the spares to the new vlan.You now know what a vlan is. They were created to make use of unused switchports and still keep network integrity between subnets because each vlan is it's own broadcast domain.What that means is, you can just assign a different subnet to those 8 devices and plug them into 8 spare ports on your switch and they will work. But anyone on the original network can see all of the traffic on the new network. There would be no isolation. Vlans are completely isolated from each other.They make 1 switch, into 2 or more logically separated switches.So now your questions.1. No rules means everything is blocked. You won't even be able to ping the interface.So you'll probably want to add some rules, like NTP for example, but up to you.2. The LAN has a default allow any rule, did you change that?If not, then you aren't configuring your vlan correctly.What model switch are you using?Do you have a separate switch for the LAN and the vlan or using the same?Did you trunk the port going to the router if using one switch?Many other questions but it would be easier to just post your config. Everything relevant.
If this is a possibility, than I have a couple more questions.1)Is there a cheat sheet somewhere where I can learn how to make such a rule? There are a lot of options that I can't understand if are useful to my use case. And besides this, what is the difference between a firewall rule and port forwarding?
2)What is a possible/common case use of a VLAN if you can achiece isolation via firewall rules in the same subnet?