If the tunnel where a PW is located is configured with Tunnel APs, the PW cannot be configured with PW APS.

Question

Options

• ATrue
• BFalse

• A
  78% (25)
• B
  22% (7)

Explanation

Option A is correct because Tunnel APS and PW APS are mutually exclusive protection mechanisms - when APS is applied at the tunnel level, fault detection and traffic switchover are already handled for all pseudowires within that tunnel, making PW-level APS redundant and technically unsupported by most implementations (such as Huawei's MPLS/PWE3 platforms). Allowing both simultaneously would create conflicting protection domains: two independent mechanisms competing to react to the same failure, which could cause packet duplication, loop conditions, or unpredictable switchover behavior. Option B is incorrect because it assumes both protection schemes can coexist, but the underlying protocol design enforces a single point of protection per service path to maintain deterministic failover.

Memory tip: Think of it as a hierarchy - protection is applied at one layer, not both. "Tunnel APS up top means PW APS must stop." If the umbrella (tunnel) already shields you, you don't open another one (PW) underneath it.

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