3Com 3C996B-T User Manual

Contents

3Com 3C996B-T User Manual Manual pdf 110 page image

A Key Protocols and Interfaces102Failover TeamingFailover Teaming provides redundant NIC operation in the event that a networkconnection fails. When multiple Gigabit Ethernet NICs are installed in the same server,they can be grouped into teams. Each team must have at least one NIC, but can supportup to eight NICs. The number of teams is limited by the number of NICs that are installed.If the primary NIC in a team is disconnected because of failure of the NIC, cable, or switchport, the secondary team member becomes active, redirecting both inbound andoutbound traffic originally assigned to the primary NIC. Sessions will be maintained,causing no impact to the user.VLANs OverviewVirtual Local Area Networks (VLANs) allow you to split your physical LAN into logicalsubparts, to create logical segmentation of workgroups and to enforce security policiesamong each logical segment. Each defined VLAN behaves as its own separate network,with its traffic and broadcasts isolated from the others, increasing bandwidth efficiencywithin each logical group. As many as 64 VLANs can be defined for each NIC on yourserver, depending on the amount of memory available in your system.Although VLANs are commonly used to create individual broadcast domains and/orseparate IP subnets, it is sometimes useful for a server to have a presence on more thanone VLAN simultaneously. Gigabit Ethernet NICs support multiple VLANs on a per-port orper-interface basis, allowing flexible network configurations.VLAN SupportVirtual Local Area Networks (VLANs) are commonly used to split up groups of networkusers into manageable broadcast domains, to create logical segmentation of workgroups,and to enforce security policies among logical segments.Each Team supports up to 64 VLANs. Note that only 3Com NICs and Alteon AceNIC NICscan be part of a team with VLANs. With multiple VLANs on a NIC, a server with a singleNIC can have a logical presence on multiple IP subnets. With multiple VLANs in a team, aserver can have a logical presence on multiple IP subnets and benefit from load balancingand failover.Adaptive Interrupt FrequencyThe NIC driver intelligently adjusts host interrupt frequency based on traffic conditions,to increase overall application throughput. When traffic is light, the NIC driver interruptsthe host for each received packet, minimizing latency. When traffic is heavy, the NICissues one host interrupt for multiple, back-to-back incoming packets, preserving hostCPU cycles.Dual DMA ChannelsThe PCI interface on the Gigabit Ethernet NIC contains two independent DMA channelsfor simultaneous read and write operations.NOTE: VLAN tagging is required to be enabled only on switch ports that createtrunk links to other switches, or on ports connected to tag-capable end-stations,such as servers or workstations with 3Com NICs.NOTE: NICs that are members of a failover team can also be configured tosupport VLANs. Because VLANs are not supported for an Intel LOM if a LOM is amember of a failover team, VLANs cannot be configured for that team.