This value records the encapsulation/tagging scheme configured on this internal backplane link, which determines how VLAN-tagged frames from multiple blade vNICs are carried over the shared IOM-to-fabric-interconnect connection. It matters on the internal Ethernet link that carries a blade's traffic from the chassis I/O Module up to a Fabric Interconnect over the backplane because a mismatched encapsulation setting between the two ends of an internal link is a common cause of a link that comes up physically but passes no traffic. On this backplane link, an encap value of dot1q confirms VLAN tags from the blade's vNICs are preserved across the backplane rather than being carried untagged.