820 Configuring Link AggregationFigure 28-1 shows an example of a switch in the wiring closet connected to aswitch in the data center by a LAG that consists of four physical 1 Gbps links.The LAG provides full-duplex bandwidth of 4 Gbps between the twoswitches.Figure 28-1. LAG ConfigurationLAGs can be configured on stand-alone or stacked switches. In a stack ofswitches, the LAG can consist of ports on a single unit or across multiplestack members. When a LAG members span different units across a stack,and a unit fails, the remaining LAG members on the functional unitscontinue to handle traffic for the LAG.Why Are Link Aggregation Groups Necessary?The primary purpose of LAGs is to increase the overall bandwidth betweentwo switches. This is accomplished by effectively aggregating multiple portstogether that act as a single, logical connection between the two switches.LAGs also provide redundancy. If a link fails, traffic is automaticallyredistributed across the remaining links.What Is the Difference Between Static and Dynamic Link Aggregation?Link aggregation can be configured as either dynamic or static. Dynamicconfiguration is supported using the IEEE 802.3ad standard, which is knownas Link Aggregation Control Protocol (LACP). Static configuration is usedwhen connecting a PowerConnect 7000 Series switch to an external GigabitEthernet switch that does not support LACP.One advantage of LACP is that the protocol enables the switch to confirmthat the external switch is also configured for link aggregation. When usingstatic configuration, a cabling or configuration mistake involving the 7000
