Your customer currently has two (2) 5406 modular switches with MSTP configured as their core switches. You are proposing a new solution. What would you explain regarding the AOS-CX VSX switch pair…

Question

Options

• AUse vsx-sync in the MSTP region configuration to get synced.
• BEnable vsx-sync stp-global in vsx mode to sync the configuration.
• CSpanning-tree configuration is synced by default with VSX.
• DEnable vsx-peer stp-global in vsx mode to sync the configuration.

• A
  3% (2)
• B
  76% (53)
• C
  7% (5)
• D
  14% (10)

Explanation

Option B is correct because in AOS-CX, STP synchronization between VSX peers is not automatic - you must explicitly enable it by entering VSX mode (router vsx) and issuing vsx-sync stp-global, which tells the VSX framework to keep spanning-tree global settings (timers, mode, priorities) consistent across both peers.

Why the distractors are wrong:

• A is wrong because vsx-sync is configured inside the VSX context, not inside the MSTP region configuration block - mixing up the configuration hierarchy.
• C is wrong because VSX does not auto-sync STP by default; only a few settings (like LAG membership) sync automatically, so leaving STP unsynced risks topology mismatches between peers.
• D is wrong because vsx-peer is not the correct command prefix for synchronization tasks - vsx-sync is the proper keyword for pushing config parity between peers.

Memory tip: Think of the rule as "VSX sync is never free for STP" - you must explicitly opt in with vsx-sync stp-global inside VSX mode, just like you'd explicitly permit VLANs on a trunk. If you remember "sync is a verb you have to say out loud," you'll eliminate both the "it's automatic" (C) and the wrong-command (D and A) distractors immediately.

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