Exactly as described, this sets the inner, or Customer, VLAN ID stamped onto generated packets, applicable when EncapType is dot1q or QinQ. Unlike SVid which only applies under QinQ, this field is relevant under both single-tag and double-tag encapsulation, making it the one VLAN ID setting an operator must get right regardless of which of those two tagging modes the profile uses. For example, a dot1q profile testing a specific customer's EVC would set this to that customer's actual assigned VLAN ID, such as 250, to correctly emulate their tagged traffic.