This holds the numeric error code returned by the remote (peer) fabric interconnect when it responded to an invocation as part of this vNet endpoint's sync process. This is the actual machine-readable error an admin or Cisco TAC uses to look up exactly why the peer fabric rejected or failed this endpoint's sync request, rather than relying on a vague 'sync failed' status alone. A non-zero value here, cross-referenced against Cisco's UCS error code list, might indicate the peer fabric interconnect rejected the request because the VLAN didn't exist locally yet.