HP Virtual Connect 8Gb 20-port Fibre Channel Module for c-Class BladeSystem - Manual (Page 84)

Virtual Connect networks 84
IGMP Snooping
The IGMP Snooping feature enables VC-Enet modules to monitor (snoop) the IGMP IP multicast membership
activities and configure hardware Layer 2 switching behavior of multicast traffic to optimize network
resource usage. IGMP v1, v2, and v3 snooping are supported.
The IGMP Snooping idle timeout interval is set to 260 seconds by default. This value is the "Group
Membership Interval" value as specified by IGMP v2 specification (RFC2236). For optimum network
resource usage, set the interval to match the configuration on the customer network's multicast router settings.
Network Loop Protection
When a link is established on a VC-Enet module port, the port exchanges LLDP packets with the far-side
connection. This LLDP protocol is an IEEE 802.1 standard that uses special BPDU packets that are not
forwarded by Ethernet bridges or switches.
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.
The loop avoidance feature cannot be disabled or changed. However, the preferred uplink connection for a
network can be identified when defining network uplinks.
VCM loop avoidance does not extend to server downlink ports. If a loop is formed on the server downlink
ports, any BPDUs traversing the VC domain from an uplink through server downlinks is transmitted back to
the uplink port on the external switch. If this external switch is enabled for BPDU loop protection, the uplink
port is disabled, causing network disruption. VCM has a network loop protection feature that provides the
ability to intercept the BPDU packets on the server downlink ports and disable the server downlink port to
prevent a loop condition. You are notified of this condition and can take action to reset the server downlink
ports.
VCM provides the ability to enable or disable network loop protection. The feature is enabled by default and
applies to all VC-Enet modules in the domain.
A reset command resets and restarts network loop protection for all server ports in a “loop-detected” error
condition.
Define Ethernet Network screen
The Define Ethernet Network screen is accessible to all users with network privileges from the Define a
Network link on the Virtual Connect Manager home page or by selecting Ethernet Network on the Define
pull-down menu.