To segment traffic on a LAN into separate broadcast domains, you create separate virtual LANs (VLANs). VLANs limit the amount of traffic flowing across the entire LAN, reducing the possible number of collisions and packet retransmissions within the LAN. For example, you might want to create a VLAN that includes the employees in a department and the resources that they use often, such as printers, servers, and so on
Also, I don't understand what you mean by this: "Most of the VLAN that I have are in L2 except the management vlan which will be an IRB".But ALL VLANs are layer 2. What might be confusing is that you configure a L3 interface to connect the vlan to layer 3 and you call it interface vlan., but that is just a name.