A storage administrator is upgrading Cisco NX-OS on a Cisco MDS switch. The administrator performs an ISSU upgrade following the configuration guide. While the install is proceeding, the…

Question

Options

• AThe fabric data plane resets as part of the upgrade process.
• BThe new server is unable to log in to the fabric to receive an FC-ID.
• CThe upgrade process disables any currently unused ports.
• DThe zoning database is locked during the upgrade process.

• A
  7% (4)
• B
  27% (16)
• C
  15% (9)
• D
  52% (31)

Explanation

During an ISSU (In-Service Software Upgrade), Cisco MDS locks the zoning database to maintain consistency across the fabric while the upgrade proceeds - meaning no new zone changes can be committed. The new server connects to the switch physically but cannot be added to any zone or have zone policy enforced for it, so it is blocked from accessing storage, while existing servers already have established zone memberships and are unaffected.

Why the distractors are wrong:

• A is wrong because ISSU is explicitly designed to keep the data plane running - that's its entire purpose, which is confirmed by the fact that existing servers continue working.
• B is wrong because FLOGI (fabric login and FC-ID assignment) is a control-plane function that can still occur during ISSU; the block is on zoning, not fabric login itself.
• C is wrong because ISSU does not disable idle ports - port state is preserved throughout the upgrade.

Memory tip: Think of ISSU as editing a shared spreadsheet - the file gets locked while the save/upgrade is in progress to prevent corruption. Anyone already in the document (existing servers) keeps working, but no new entries (new servers needing zone records) can be written until the lock is released.

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