This string is the vendor identifier of the hardware component underlying this internal link, as tracked on the Fabric Interconnect side. It matters on the same internal chassis backplane link, but the record kept on the Fabric Interconnect (switch) side rather than the IOM/server side because it confirms whether the transceiver installed on the fabric-interconnect end is Cisco-qualified, which affects support eligibility and, on some firmware, whether the port comes up at all. A vendor value that doesn't match Cisco on this link's fabric-interconnect side is a direct explanation for an otherwise unexplained unsupported-transceiver fault on the fabric-interconnect side of this connection.