For a private VLAN (PVLAN) to span multiple switches, both the primary and secondary VLANs must be configured on all participating switches. Critically, each secondary VLAN (whether community or isolated) must be configured with its own unique 802.1Q VLAN ID (tag). This tag allows the trunk link between the switches to identify and carry the secondary VLAN traffic. The receiving switch uses this tag to map the traffic to the correct local PVLAN subdomain. Without an associated 802.1Q tag, the secondary VLAN is only a logical construct on the local switch and cannot be propagated across the network.

A. The primary (parent) and secondary VLANs must have different, unique 802.1Q tags to function correctly. Using the same tag would create a configuration conflict.

C. Stripping the 802.1Q tag would make the traffic untagged on the trunk, preventing the receiving switch from identifying which VLAN the frames belong to.

D. Changing the VLAN type from community to isolated alters its communication rules but does not solve the fundamental inter-switch transport and tagging problem.

1. Juniper Networks TechLibrary, Junos OS for EX Series. Understanding and Configuring Private VLANs on EX Series Switches. In the "Configuration Overview" section, it states: "You configure secondary VLANs by creating VLANs and specifying them as either an isolated VLAN or a community VLAN. You must also specify a VLAN ID for each secondary VLAN." This confirms the requirement for a tag.

2. Juniper Networks TechLibrary, Junos OS for EX Series. Example: Configuring a Private VLAN Spanning Multiple Switches. The configuration example explicitly shows the creation of secondary VLANs with unique vlan-id statements (e.g., set vlans community-vlan-101 vlan-id 101). This demonstrates that for inter-switch functionality, the secondary VLAN must have an associated tag.

3. Juniper Networks TechLibrary, Junos OS Switching Configuration Guide. Private VLANs Overview. Under the "PVLANs Spanning Multiple Switches" subsection, the guide explains that for PVLANs to span switches, you must "configure the primary and secondary VLANs on all switches," which inherently means defining them with their respective VLAN IDs.