Load sharing

Brocade devices can load share among up to eight equal-cost IP routes to a destination. By default, IP load sharing is enabled. The default is 4 equal-cost paths but you can specify from 2 to 8 paths.

On the ICX 7750 device, the value range for the maximum number of load-sharing paths is from 2 through 32 ,which is controlled by the system-max max-ecmp command.

The device software can use the route information it learns through OSPF to determine the paths and costs.

Figure 27  Example OSPF network with four equal-cost paths

The device has four paths to R1:

• Router ->R3
• Router ->R4
• Router ->R5
• Router ->R6

Normally, the device chooses the path to the R1 with the lower metric. For example, if the metric for R3 is 1400 and the metric for R4 is 600, the device always chooses R4.

However, suppose the metric is the same for all four routers in this example. If the costs are the same, the device now has four equal-cost paths to R1. To allow the device to load share among the equal cost routes, enable IP load sharing. Four equal-cost OSPF paths are supported by default when you enable load sharing.

OSPF load sharing is enabled by default when IP load sharing is enabled.