Specifications

HP Virtual Connect for Cisco Network Administrators (version 1.2x) page 17
VC Uplinks and VLAN Trunking
Virtual Connect supports VLAN tagging (trunking) on VC uplinks using IEEE 802.1Q and can be
configured to support VLAN tagging on blade server NIC ports.
VC Uplinks can operate in one of three modes:
• VLAN trunking mode
o Shared Uplink Set (SUS) plus tagging on external switch port
o When a VC uplink is a member of a SUS and is connected to a VLAN trunk port on an
external switch, it operates as a VLAN trunk port.
o Multiple vNets, multiple VLANs
o No tagging on server NIC ports
o Example: VC Uplink 3 in figure below
• VLAN tunneling mode
o single vNet plus tagging on external switch port
o When a VC uplink is a member of a single vNet and is connected to a VLAN trunk
port on an external switch, it operates in a mode that is equivalent to ‘dot1qtunnel’
mode on a Cisco switch.
o Single vNet, multiple VLANs
o Tagging on server NIC ports
o Example: VC Uplink 2 in figure below
• Access mode
o single vNet plus no tagging on external switch port
o When a VC uplink is a member of a single vNet and is connected to an external
switch port in access mode, it operates in a mode that is equivalent to ‘access’
mode on a Cisco switch.
o Single vNet, single VLAN
o No tagging on server NIC Ports
o Example: VC Uplink 1 in figure below
When VC is configured to support VLAN tagging on a VC uplink (VLAN trunking mode), this means
that VC is interpreting (i.e. removing and inserting tags, classifying the frame’s vNet membership
based on tag info) the tag and is a termination point for the tag (i.e. the servers do not see the
VLAN tag). This is accomplished on VC by using “Shared Uplink Sets”, or SUS for short. A SUS is one or
more VC uplinks that are configured as VLAN trunks (tagging) and correlate external VLANs to
specific vNets within the VC Domain. The Administrator creates the SUS, adds one or more VC
uplinks, defines which VLAN tags are carried on the VC uplinks and then provides a vNet name
(ASCII) for each of the VLANs defined. This means that the uplink ports within the SUS provide
external connectivity for multiple vNets. In other words, one or more vNets share a set of uplinks for
external network connectivity. This is why the term “Shared Uplink Sets” is used. See VC Uplink 3 in
the figure below.
When VC uplink ports are assigned to a single vNet and connected to an external switch port in
VLAN trunking mode, the VC uplink and vNet operate in VLAN\CoS tunneling mode or dot1qtunnel
mode by default. In other words, the vNet keeps all frames within the same layer 2 domain (vNet),
however, VC allows the frames to carry different VLAN tags from the external network all the way to
the server NIC ports and vice versa. See VC Uplink 2 in the figure below. When VC uplink ports are
assigned to a single vNet and connected to an external switch port in access mode, the VC uplink
and vNet operate in access mode only carries untagged frames for a single VLAN (the access VLAN
on the switch). See VC Uplink 1 in the figure below. In other words, depending on the configuration