To evaluate Layer 3 traffic between VLANs, you should create a family inet firewall filter with the appropriate match criteria and actions. This is because Layer 3 filtering involves IP-based traffic evaluation, which falls under family inet. Additionally, you should apply the firewall filter to the appropriate IRB (Integrated Routing and Bridging) interface, as the IRB interface bridges the VLANs and allows for routing between them. This enables the firewall filter to inspect and act on the inter-VLAN traffic.