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User Guide NetXtreme II

September 2013

Broadcom Corporation

Document INGSRVT78-CDUM100-R General Network Considerations Page 43

Topology Change Notice BPDUs are sent when a port that was forwarding changes to blocking or transitions to forwarding.

A TCN BPDU does not initiate an STP recalculation. It only affects the aging time of the forwarding table entries in the

switch.It will not change the topology of the network or create loops. End nodes such as servers or clients trigger a topology

change when they power off and then power back on.

Port Fast/Edge Port

To reduce the effect of TCNs on the network (for example, increasing flooding on switch ports), end nodes that are powered

on/off often should use the Port Fast or Edge Port setting on the switch port they are attached to. Port Fast or Edge Port is

a command that is applied to specific ports and has the following effects:

• Ports coming from link down to link up will be put in the forwarding STP mode instead of going from listening to learning

and then to forwarding. STP is still running on these ports.

• The switch does not generate a Topology Change Notice when the port is going up or down.

LAYER 3 ROUTING/SWITCHING

The switch that the teamed ports are connected to must not be a Layer 3 switch or router. The ports in the team must be in

the same network.

TEAMING WITH HUBS (FOR TROUBLESHOOTING PURPOSES ONLY)

• Hub Usage in Teaming Network Configurations

• SLB Teams

• SLB Team Connected to a Single Hub

• Generic and Dynamic Trunking (FEC/GEC/IEEE 802.3ad)

SLB teaming can be used with 10/100 hubs, but it is only recommended for troubleshooting purposes, such as connecting

a network analyzer in the event that switch port mirroring is not an option.

Hub Usage in Teaming Network Configurations

Although the use of hubs in network topologies is functional in some situations, it is important to consider the throughput

ramifications when doing so. Network hubs have a maximum of 100 Mbps half-duplex link speed, which severely degrades

performance in either a Gigabit or 100 Mbps switched-network configuration. Hub bandwidth is shared among all connected

devices; as a result, when more devices are connected to the hub, the bandwidth available to any single device connected

to the hub is reduced in direct proportion to the number of devices connected to the hub.

It is not recommended to connect team members to hubs; only switches should be used to connect to teamed ports. An SLB

team, however, can be connected directly to a hub for troubleshooting purposes. Other team types can result in a loss of

connectivity if specific failures occur and should not be used with hubs.

SLB Teams

SLB teams are the only teaming type not dependant on switch configuration. The server intermediate driver handles the load

balancing and fault tolerance mechanisms with no assistance from the switch. These elements of SLB make it the only team

type that maintains failover and fallback characteristics when team ports are connected directly to a hub.

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Dell Broadcom NetXtreme Family of Adapters Betriebsanweisung Seite 43