HP Virtual Connect for c-Class BladeSystem Setup and Installation Guide

Installation 24
Single enclosure stacking diagram
Modules (top to
bottom)
Ethernet Modules
*HP 1/10Gb VC-Enet Modules and HP 1/10 Gb-F Ethernet Modules are not supported as primary and backup modules
in multi-enclosure configurations. For optimal VC Manager performance, HP Virtual Connect FlexFabric 10Gb/24-port
Modules or HP Virtual Connect Flex-10 10Gb Ethernet Modules should be designated as primary and backup modules
over HP 1/10Gb VC-Enet Modules and HP 1/10 Gb-F Ethernet Modules in a single-enclosure configuration, when
possible.
VC-Enet modules support 0.5 m to 7 m (1.64 ft to 23.00 ft) 10GBASE-CX4 stacking cables. The 1000BASE-T
links can also be used as stacking links of up to 100 m (328 ft). Ports with different connector types can be
aggregated if the link speed is the same. For example, CX4 and SFP+ ports both running at 10G can be
aggregated to provide enhanced throughput for the stacking link.
NOTE: The CX4 interface uses the same physical connector as Infiniband, but Infiniband cables
are tuned differently and will not perform as well in CX4 applications. HP recommends
purchasing CX4 cable assemblies that meet the IEEE CX4 specifications and support 10-Gigabit
communication at distances from 3 m to 15 m (9.84 ft to 49.20 ft).
FlexFabric modules support DAC cables. Uplink ports X1-X4 only support 0.5 m to 5m (1.64 ft to 16.40 ft)
DAC stacking or uplink cables. Uplink Ports X5-X8 support 0.5 m to 7 m (1.64 ft to 23.00 ft) DAC stacking
or uplink cables.
HP recommends fully redundant interconnection of VC-Enet modules. The recommended stacking
configurations have redundant connections. If a stacking cable is disconnected or fails, the Ethernet packets
within the Virtual Connect domain are automatically re-routed to the uplink through the redundant path. This
configuration also helps preserve network connectivity if an Ethernet interconnect module fails or is removed.
Network loop protection
To avoid network loops, Virtual Connect first verifies that only one active uplink exists per network from the
Virtual Connect domain to the external Ethernet switching environment. Second, Virtual Connect makes sure
that no network loops are created by the stacking links between Virtual Connect modules.
• One active link—A VC uplink set can include multiple uplink ports. To prevent a loop with broadcast
traffic coming in one uplink and going out another, only one uplink or uplink LAG is active at a time. The
uplink or LAG with the greatest bandwidth should be selected as the active uplink. If the active uplink
loses the link, then the next best uplink is made active.
• No loops through stacking links—If multiple VC-Enet modules are used, they are interconnected using
stacking links, which might appear as an opportunity for loops within the VC environment. For each
individual network in the Virtual Connect environment, VC blocks certain stacking links to ensure that
each network has a loop-free topology.
Enhanced network loop protection detects loops on downlink ports, which can be a Flex-10 logical port or
physical port. The feature applies to Flex-10 logical function if the Flex-10 port is operating under the control
of DCC protocol. If DCC is not available, the feature applies to a physical downlink port.
Enhanced network loop protection uses two methods to detect loops:
• It periodically injects a special probe frame into the VC domain and monitors downlink ports for the
looped back probe frame. If this special probe frame is detected on downlink ports, the port is
considered to cause the loop condition.