HP Virtual Connect for c-Class BladeSystem Version 4.01 User Guide

Virtual Connect networks 98
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Set maximum connection speed. This value is the maximum speed for server profile connections
mapped to this network. This speed limits the maximum port speed from the server to the network
connection associated with the multiple networks.
Click Apply.
Virtual Connect can only control link speed for Flex-10 NICs when they are connected to an HP Virtual
Connect Flex-10 Module. Virtual Connect cannot control the link speed of traditional NICs. For more
information, see "Flex-10 overview (on page 163)."
IMPORTANT: Each FlexNIC and FlexHBA is recognized by the server as a PCIe physical function
device with adjustable speeds from 100Mb to 10Gb in 100Mb increments when connected to an
NC553i/m 10Gb 2-port FlexFabric Converged Network Adapter or any Flex-10 NIC. For
NC551i/m Dual Port FlexFabric 10Gb Converged Network Adapters, the range is limited to
1Gb to 10Gb in 100Mb increments.
MAC Cache Failover
When a VC-Enet uplink that was previously in standby mode becomes active, external Ethernet switches can
take several minutes to recognize that the c-Class server blades can now be reached on this newly active
connection. Enabling Fast MAC Cache Failover causes Virtual Connect to transmit Ethernet packets on newly
active links, which enables the external Ethernet switches to identify the new connection and update their
MAC caches appropriately. This transmission sequence repeats a few times at the MAC refresh interval (HP
recommends 5 seconds) and completes in about 1 minute.
Virtual Connect only transmits MAC Cache update frames on VLANs that have been configured in the VC
domain. The update frames are VLAN tagged appropriately for networks defined on shared uplink sets. For
dedicated networks, only untagged update frames are generated, regardless of whether or not VLAN
Tunneling is enabled. In a VLAN tunnel, all customer VLAN tags pass through Virtual Connect transparently.
Virtual Connect does not examine nor record VLAN tag information in tunneled networks; therefore, it cannot
generate tagged update frames.
IMPORTANT:
Be sure to set switches to allow MAC addresses to move from one port to another
without waiting for an expiration period or causing a lock out.
Always enable the "spanning tree portfast" feature to allow the switch port to bypass the
"listening" and "learning" stages of spanning tree and quickly transition to the "forwarding"
stage, allowing edge devices to immediately begin communication on the network.
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.