What is true about clients located in isolated VLAN?

Question

Options

• ABy default, The switch allows ARP traffic between clients in isolated VLAN
• BEndpoints in an isolated VLAN are not allowed to communicate with each other
• CIsolated VLAN is always a member of Service VLAN
• DIsolated VLAN is a VLAN in QinQ

• A
  6% (1)
• B
  94% (16)

Explanation

Option B is correct because an isolated VLAN is a Private VLAN (PVLAN) secondary VLAN type where member ports are completely blocked from Layer 2 communication with one another - they can only send traffic to a promiscuous port (typically a router or gateway), not to other hosts in the same isolated VLAN.

Why the distractors are wrong:

• A is false: ARP is Layer 2 traffic, and isolated VLAN ports block all inter-host L2 traffic by design - there is no ARP exception.
• C is false: Isolated VLANs are secondary VLANs mapped to a primary VLAN in PVLAN architecture; "Service VLAN" is a QinQ/802.1ad concept, not PVLAN terminology.
• D is false: Isolated VLANs belong to the PVLAN (Private VLAN) framework (RFC 5517), not QinQ (802.1ad), which uses S-VLANs and C-VLANs for double-tagging.

Memory tip: Associate "isolated" with solitary confinement - hosts in an isolated VLAN are locked in individual cells and can only communicate with the warden (the promiscuous port/gateway), never with each other.

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